From 9fe8adf35c16ab5d4566b03f3b36863c90b5b6dd Mon Sep 17 00:00:00 2001 From: Hans Bolinder Date: Thu, 12 Mar 2015 15:35:13 +0100 Subject: Update Erlang Reference Manual Language cleaned up by the technical writers xsipewe and tmanevik from Combitech. Proofreading and corrections by Hans Bolinder. --- system/doc/reference_manual/character_set.xml | 18 +- system/doc/reference_manual/code_loading.xml | 117 ++-- system/doc/reference_manual/data_types.xml | 164 +++--- system/doc/reference_manual/distributed.xml | 120 +++-- system/doc/reference_manual/errors.xml | 67 +-- system/doc/reference_manual/expressions.xml | 732 ++++++++++++++------------ system/doc/reference_manual/functions.xml | 79 +-- system/doc/reference_manual/introduction.xml | 53 +- system/doc/reference_manual/macros.xml | 75 +-- system/doc/reference_manual/modules.xml | 153 +++--- system/doc/reference_manual/patterns.xml | 2 +- system/doc/reference_manual/ports.xml | 114 ++-- system/doc/reference_manual/processes.xml | 89 ++-- system/doc/reference_manual/records.xml | 66 +-- system/doc/reference_manual/typespec.xml | 230 ++++---- 15 files changed, 1162 insertions(+), 917 deletions(-) (limited to 'system') diff --git a/system/doc/reference_manual/character_set.xml b/system/doc/reference_manual/character_set.xml index b09b484582..d6989373bf 100644 --- a/system/doc/reference_manual/character_set.xml +++ b/system/doc/reference_manual/character_set.xml @@ -4,7 +4,7 @@
- 20142014 + 20142015 Ericsson AB. All Rights Reserved. @@ -31,7 +31,7 @@
Character Set -

In Erlang 4.8/OTP R5A the syntax of Erlang tokens was extended to +

Since Erlang 4.8/OTP R5A, the syntax of Erlang tokens is extended to allow the use of the full ISO-8859-1 (Latin-1) character set. This is noticeable in the following ways:

@@ -98,7 +98,7 @@ ø - ÿ Lowercase letters - Character Classes. + Character Classes

In Erlang/OTP R16B the syntax of Erlang tokens was extended to handle Unicode. The support is limited to @@ -111,13 +111,13 @@

Source File Encoding -

The Erlang source file encoding is selected by a + +

The Erlang source file encoding is selected by a comment in one of the first two lines of the source file. The first string that matches the regular expression coding\s*[:=]\s*([-a-zA-Z0-9])+ selects the encoding. If - the matching string is not a valid encoding it is ignored. The - valid encodings are Latin-1 and UTF-8 where the + the matching string is an invalid encoding, it is ignored. The + valid encodings are Latin-1 and UTF-8, where the case of the characters can be chosen freely.

The following example selects UTF-8 as default encoding:

@@ -127,7 +127,7 @@
 %% For this file we have chosen encoding = Latin-1
 %% -*- coding: latin-1 -*-
-

The default encoding for Erlang source files was changed from - Latin-1 to UTF-8 in Erlang OTP 17.0.

+

The default encoding for Erlang source files is changed from + Latin-1 to UTF-8 since Erlang/OTP 17.0.

diff --git a/system/doc/reference_manual/code_loading.xml b/system/doc/reference_manual/code_loading.xml index b5b5704df5..48ec32d6df 100644 --- a/system/doc/reference_manual/code_loading.xml +++ b/system/doc/reference_manual/code_loading.xml @@ -4,7 +4,7 @@
- 20032014 + 20032015 Ericsson AB. All Rights Reserved. @@ -29,35 +29,39 @@ code_loading.xml

How code is compiled and loaded is not a language issue, but - is system dependent. This chapter describes compilation and - code loading in Erlang/OTP with pointers to relevant parts of + is system-dependent. This section describes compilation and + code loading in Erlang/OTP with references to relevant parts of the documentation.

Compilation

Erlang programs must be compiled to object code. - The compiler can generate a new file which contains the object - code. The current abstract machine which runs the object code is + The compiler can generate a new file that contains the object + code. The current abstract machine, which runs the object code, is called BEAM, therefore the object files get the suffix .beam. The compiler can also generate a binary which can be loaded directly.

-

The compiler is located in the Kernel module compile, see - compile(3).

+

The compiler is located in the module compile (see the + compile(3) manual page in + Compiler).

 compile:file(Module)
 compile:file(Module, Options)

The Erlang shell understands the command c(Module) which both compiles and loads Module.

-

There is also a module make which provides a set of - functions similar to the UNIX type Make functions, see - make(3).

-

The compiler can also be accessed from the OS prompt, see - erl(1).

+

There is also a module make, which provides a set of + functions similar to the UNIX type Make functions, see the + make(3) + manual page in Tools.

+

The compiler can also be accessed from the OS prompt, see the + erl(1) manual page in ERTS.

 % erl -compile Module1...ModuleN
 % erl -make

The erlc program provides an even better way to compile - modules from the shell, see erlc(1). It understands a + modules from the shell, see the + erlc(1) manual page in ERTS. + It understands a number of flags that can be used to define macros, add search paths for include files, and more.

@@ -68,13 +72,17 @@ compile:file(Module, Options)
Code Loading

The object code must be loaded into the Erlang runtime - system. This is handled by the code server, see - code(3).

-

The code server loads code according to a code loading strategy + system. This is handled by the code server, see the + code(3) + manual page in Kernel.

+

The code server loads code according to a code loading strategy, which is either interactive (default) or - embedded. In interactive mode, code are searched for in + embedded. In interactive mode, code is searched for in a code path and loaded when first referenced. In - embedded mode, code is loaded at start-up according to a boot script. This is described in System Principles.

+ embedded mode, code is loaded at start-up according to a + boot script. This is described in + + System Principles .

@@ -86,16 +94,17 @@ compile:file(Module, Options) the system for the first time, the code becomes 'current'. If then a new instance of the module is loaded, the code of the previous instance becomes 'old' and the new instance becomes 'current'.

-

Both old and current code is valid, and may be evaluated +

Both old and current code is valid, and can be evaluated concurrently. Fully qualified function calls always refer to - current code. Old code may still be evaluated because of processes + current code. Old code can still be evaluated because of processes lingering in the old code.

-

If a third instance of the module is loaded, the code server will - remove (purge) the old code and any processes lingering in it will - be terminated. Then the third instance becomes 'current' and +

If a third instance of the module is loaded, the code server + removes (purges) the old code and any processes lingering in it is + terminated. Then the third instance becomes 'current' and the previously current code becomes 'old'.

To change from old code to current code, a process must make a - fully qualified function call. Example:

+ fully qualified function call.

+

Example:

 -module(m).
 -export([loop/0]).
@@ -109,60 +118,62 @@ loop() ->
             loop()
     end.

To make the process change code, send the message - code_switch to it. The process then will make a fully - qualified call to m:loop() and change to current code. - Note that m:loop/0 must be exported.

-

For code replacement of funs to work, the syntax - fun Module:FunctionName/Arity should be used.

+ code_switch to it. The process then makes a fully + qualified call to m:loop() and changes to current code. + Notice that m:loop/0 must be exported.

+

For code replacement of funs to work, use the syntax + fun Module:FunctionName/Arity.

- Running a function when a module is loaded + Running a Function When a Module is Loaded -

The on_load feature should be considered experimental - as there are a number of known weak points in current semantics - which therefore might also change in future releases:

+

The on_load feature is to be considered experimental + as there are a number of known weak points in current semantics, + which therefore might change in future Erlang/OTP releases:

-

Doing external call in on_load to the module itself +

Doing external call in on_load to the module itself leads to deadlock.

At module upgrade, other processes calling the module - get suspended waiting for on_load to finish. This can be very bad + get suspended waiting for on_load to finish. This can be very bad for applications with demands on realtime characteristics.

 -

At module upgrade, no rollback is done if the on_load function fails. - The system will be left in a bad limbo state without any working +

At module upgrade, no rollback is done if the + on_load function fails. + The system is left in a bad limbo state without any working and reachable instance of the module.

 -

The problems with module upgrade described above could be fixed in future - releases by changing the behaviour to not make the module reachable until - after the on_load function has successfully returned.

+

The problems with module upgrade described above can be fixed in future + Erlang/OTP releases by changing the behaviour to not make the module reachable until + after the on_load function has successfully returned.

 -

The -on_load() directive names a function that should - be run automatically when a module a loaded. Its syntax is:

+

The -on_load() directive names a function that is to + be run automatically when a module is loaded.

+

Its syntax is as follows:

 -on_load(Name/0).
-

It is not necessary to export the function. It will be called in a - freshly spawned process (which will be terminated as soon as the function +

It is not necessary to export the function. It is called in a + freshly spawned process (which terminates as soon as the function returns). The function must return ok if the module is to - be remained loaded and become callable, or any other value if the module - is to be unloaded. Generating an exception will also cause the + remain loaded and become callable, or any other value if the module + is to be unloaded. Generating an exception also causes the module to be unloaded. If the return value is not an atom, - a warning error report will be sent to the error logger.

+ a warning error report is sent to the error logger.

A process that calls any function in a module whose on_load - function has not yet returned will be suspended until the on_load + function has not yet returned, is suspended until the on_load function has returned.

-

In embedded mode, all modules will be loaded first and then - will all on_load functions be called. The system will be - terminated unless all of the on_load functions return +

In embedded mode, first all modules are loaded. + Then all on_load functions are called. The system is + terminated unless all of the on_load functions return ok

. -

Example:

+

Example:

 -module(m).
@@ -174,7 +185,7 @@ load_my_nifs() ->
     erlang:load_nif(NifPath, Info).

If the call to erlang:load_nif/2 fails, the module - will be unloaded and there will be warning report sent to + is unloaded and a warning report is sent to the error loader.

diff --git a/system/doc/reference_manual/data_types.xml b/system/doc/reference_manual/data_types.xml index 37c0db5ff7..6226fa2f31 100644 --- a/system/doc/reference_manual/data_types.xml +++ b/system/doc/reference_manual/data_types.xml @@ -4,7 +4,7 @@
- 20032013 + 20032015 Ericsson AB. All Rights Reserved. @@ -28,12 +28,12 @@ data_types.xml
+

Erlang provides a number of data types, which are listed in + this section.

Terms -

Erlang provides a number of data types which are listed in this - chapter. A piece of data of any data type is called a - term.

+

A piece of data of any data type is called a term.

@@ -44,16 +44,17 @@ $char

- ASCII value of the character char. + ASCII value or unicode code-point of the character + char. base#value

- Integer with the base base, which must be an + Integer with the base base, that must be an integer in the range 2..36.

In Erlang 5.2/OTP R9B and earlier versions, the allowed range is 2..16. -

Examples:

+

Examples:

 1> 42.
 42
@@ -75,11 +76,11 @@
 
   

     Atom
-    
An atom is a literal, a constant with name. An atom should be
+    
An atom is a literal, a constant with name. An atom is to be
       enclosed in single quotes (') if it does not begin with a
       lower-case letter or if it contains other characters than
       alphanumeric characters, underscore (_), or @.

-    
Examples:

+    
Examples:

     
 hello
 phone_number
@@ -90,11 +91,11 @@ phone_number
   

     Bit Strings and Binaries
     
A bit string is used to store an area of untyped memory.

-    
Bit Strings are expressed using the
+    
Bit strings are expressed using the
       bit syntax.

-    
Bit Strings which consists of a number of bits which is evenly 
-      divisible by eight are called Binaries

-    
Examples:

+    
Bit strings that consist of a number of bits that are evenly
+      divisible by eight, are called binaries

+    
Examples:

     
 1> <<10,20>>.
 <<10,20>>
@@ -102,12 +103,14 @@ phone_number
 <<"ABC">>
 1> <<1:1,0:1>>.
 <<2:2>>

-    
More examples can be found in Programming Examples.

+    
For more examples,
+      see 
+      Programming Examples.

   

 
   

     Reference
-    
A reference is a term which is unique in an Erlang runtime
+    
A reference is a term that is unique in an Erlang runtime
       system, created by calling make_ref/0.

   

 
@@ -116,34 +119,42 @@ phone_number
     
A fun is a functional object. Funs make it possible to create
       an anonymous function and pass the function itself -- not its
       name -- as argument to other functions.

-    
Example:

+    
Example:

     
 1> Fun1 = fun (X) -> X+1 end.
 #Fun<erl_eval.6.39074546>
 2> Fun1(2).
 3

-    
Read more about funs in Fun Expressions. More examples can be found in Programming
-      Examples.

+    
Read more about funs in 
+      Fun Expressions. For more examples, see
+      
+      Programming Examples.

   

 
   

     Port Identifier
-    
A port identifier identifies an Erlang port. open_port/2,
-      which is used to create ports, will return a value of this type.

+    
A port identifier identifies an Erlang port.

+    
open_port/2, which is used to create ports, returns
+      a value of this data type.

     
Read more about ports in Ports and Port Drivers.

   

 
   

     Pid
-    
A process identifier, pid, identifies a process.
-      spawn/1,2,3,4, spawn_link/1,2,3,4 and
-      spawn_opt/4, which are used to create processes, return
-      values of this type. Example:

+    
A process identifier, pid, identifies a process.

+    
The following BIFs, which are used to create processes, return
+      values of this data type:

+    
+      spawn/1,2,3,4
+      spawn_link/1,2,3,4
+      spawn_opt/4
+    
+    
Example:

     
 1> spawn(m, f, []).
 <0.51.0>

-    
The BIF self() returns the pid of the calling process.
-      Example:

+    
In the following example, the BIF self() returns
+      the pid of the calling process:

     
 -module(m).
 -export([loop/0]).
@@ -166,14 +177,14 @@ who_are_you

 
   

     Tuple
-    
Compound data type with a fixed number of terms:

+    
A tuple is a compound data type with a fixed number of terms:

     
 {Term1,...,TermN}

     
Each term Term in the tuple is called an
       element. The number of elements is said to be
       the size of the tuple.

     
There exists a number of BIFs to manipulate tuples.

-    
Examples:

+    
Examples:

     
 1> P = {adam,24,{july,29}}.
 {adam,24,{july,29}}
@@ -191,7 +202,8 @@ adam
 
   

     Map
-    
Compound data type with a variable number of key-value associations:

+    
A map is a compound data type with a variable number of
+      key-value associations:

     
 #{Key1=>Value1,...,KeyN=>ValueN}

 	
Each key-value association in the map is called an
@@ -199,7 +211,7 @@ adam
 		called elements. The number of association pairs is said to be
       the size of the map.

     
There exists a number of BIFs to manipulate maps.

-    
Examples:

+    
Examples:

     
 1> M1 = #{name=>adam,age=>24,date=>{july,29}}.
 #{age => 24,date => {july,29},name => adam}
@@ -214,16 +226,18 @@ adam
 6> map_size(#{}).
 0

     
A collection of maps processing functions can be found in
-	the STDLIB module maps.

-    
Read more about Maps.

+      maps manual page
+      in STDLIB.

+    
Read more about maps in 
+      Map Expressions.

   
-	  
Maps are considered experimental during OTP 17.

+    
Maps are considered to be experimental during Erlang/OTP R17.

   
   

 
   

     List
-    
Compound data type with a variable number of terms.

+    
A list is a compound data type with a variable number of terms.

     
 [Term1,...,TermN]

     
Each term Term in the list is called an
@@ -231,20 +245,21 @@ adam
       the length of the list.

     
Formally, a list is either the empty list [] or
       consists of a head (first element) and a tail
-      (remainder of the list) which is also a list. The latter can
+      (remainder of the list).
+      The tail is also a list. The latter can
       be expressed as [H|T]. The notation
-      [Term1,...,TermN] above is actually shorthand for
+      [Term1,...,TermN] above is equivalent with
       the list [Term1|[...|[TermN|[]]]].

-    
Example:      


-[] is a list, thus      


+    
Example:

+
[] is a list, thus      


 [c|[]] is a list, thus      


 [b|[c|[]]] is a list, thus      


-[a|[b|[c|[]]]] is a list, or in short [a,b,c].

-    

+[a|[b|[c|[]]]] is a list, or in short [a,b,c]

+
     
A list where the tail is a list is sometimes called a proper list. It is allowed to have a list where the tail is not a
-      list, for example [a|b]. However, this type of list is of
+      list, for example, [a|b]. However, this type of list is of
       little practical use.

-    
Examples:

+    
Examples:

     
 1> L1 = [a,2,{c,4}].
 [a,2,{c,4}]
@@ -261,18 +276,19 @@ a
 7> length([]).
 0

     
A collection of list processing functions can be found in
-      the STDLIB module lists.

+      the lists manual
+      page in STDLIB.

   

 
   

     String
     
Strings are enclosed in double quotes ("), but is not a
-      data type in Erlang. Instead a string "hello" is
-      shorthand for the list [$h,$e,$l,$l,$o], that is
+      data type in Erlang. Instead, a string "hello" is
+      shorthand for the list [$h,$e,$l,$l,$o], that is,
       [104,101,108,108,111].

     
Two adjacent string literals are concatenated into one. This is
-      done at compile-time and does not incur any runtime overhead.
-      Example:

+      done in the compilation, thus, does not incur any runtime overhead.

+      
Example:

     
 "string" "42"

     
is equivalent to

@@ -284,12 +300,13 @@ a
     Record
     
A record is a data structure for storing a fixed number of
       elements. It has named fields and is similar to a struct in C.
-      However, record is not a true data type. Instead record
+      However, a record is not a true data type. Instead, record
       expressions are translated to tuple expressions during
       compilation. Therefore, record expressions are not understood by
-      the shell unless special actions are taken. See shell(3)
-      for details.

-    
Examples:

+      the shell unless special actions are taken. For details, see the
+      shell(3) manual
+      page in STDLIB).

+    
Examples:

     
 -module(person).
 -export([new/2]).
@@ -303,14 +320,15 @@ new(Name, Age) ->
 {person,ernie,44}

     
Read more about records in
       Records. More examples can be
-      found in Programming Examples.

+      found in 
+      Programming Examples.

   

 
   

     Boolean
     
There is no Boolean data type in Erlang. Instead the atoms
       true and false are used to denote Boolean values.

-    
Examples:

+    
Examples:

     
 1> 2 =< 3.
 true
@@ -329,76 +347,80 @@ true

       
       
         \b
-        backspace
+        Backspace
       
       
         \d
-        delete
+        Delete
       
       
         \e
-        escape
+        Escape
       
       
         \f
-        form feed
+        Form feed
       
       
         \n
-        newline
+        Newline
       
       
         \r
-        carriage return
+        Carriage return
       
       
         \s
-        space
+        Space
       
       
         \t
-        tab
+        Tab
       
       
         \v
-        vertical tab
+        Vertical tab
       
       
         \XYZ, \YZ, \Z
-        character with octal representation XYZ, YZ or Z
+        Character with octal
+        representation XYZ, YZ or Z
       
       
         \xXY
-        character with hexadecimal representation XY
+        Character with hexadecimal
+        representation XY
       
       
         \x{X...}
-        character with hexadecimal representation; X... is one or more hexadecimal characters
+        Character with hexadecimal
+        representation; X... is one or more hexadecimal characters
       
       
         \^a...\^z        


 \^A...\^Z
-        control A to control Z
+        Control A to control Z
       
       
         \'
-        single quote
+        Single quote
       
       
         \"
-        double quote
+        Double quote
       
       
         \\
-        backslash
+        Backslash
       
-      Recognized Escape Sequences.
+      Recognized Escape Sequences
     
   

 
   

     Type Conversions
-    
There are a number of BIFs for type conversions. Examples:

+    
There are a number of BIFs for type conversions.

+    
Examples:

     
 1> atom_to_list(hello).
 "hello"
diff --git a/system/doc/reference_manual/distributed.xml b/system/doc/reference_manual/distributed.xml
index 88f98bc106..fb83e356f9 100644
--- a/system/doc/reference_manual/distributed.xml
+++ b/system/doc/reference_manual/distributed.xml
@@ -4,7 +4,7 @@
 
   

     
-      20032013
+      20032015
       Ericsson AB. All Rights Reserved.
     
     
@@ -36,22 +36,24 @@
       runtime system is called a node. Message passing between
       processes at different nodes, as well as links and monitors, are
       transparent when pids are used. Registered names, however, are
-      local to each node. This means the node must be specified as well
-      when sending messages etc. using registered names.

+      local to each node. This means that the node must be specified as well
+      when sending messages, and so on, using registered names.

     
The distribution mechanism is implemented using TCP/IP sockets.
-      How to implement an alternative carrier is described in ERTS User's Guide.

+      How to implement an alternative carrier is described in the
+      ERTS User's Guide.

   

 
   

     Nodes
-    
A node is an executing Erlang runtime system which has
-      been given a name, using the command line flag -name
+    
A node is an executing Erlang runtime system that has
+      been given a name, using the command-line flag -name
       (long names) or -sname (short names).

-    
The format of the node name is an atom name@host where
-      name is the name given by the user and host is
+    
The format of the node name is an atom name@host.
+      name is the name given by the user. host is
       the full host name if long names are used, or the first part of
       the host name if short names are used. node() returns
-      the name of the node. Example:

+      the name of the node.

+      
Example:

     
 % erl -name dilbert
 (dilbert@uab.ericsson.se)1> node().
@@ -69,16 +71,16 @@ dilbert@uab

   

     Node Connections
     
The nodes in a distributed Erlang system are loosely connected.
-      The first time the name of another node is used, for example if
+      The first time the name of another node is used, for example, if
       spawn(Node,M,F,A) or net_adm:ping(Node) is called,
-      a connection attempt to that node will be made.

+      a connection attempt to that node is made.

     
Connections are by default transitive. If a node A connects to
-      node B, and node B has a connection to node C, then node A will
-      also try to connect to node C. This feature can be turned off by
-      using the command line flag -connect_all false, see
-      erl(1).

+      node B, and node B has a connection to node C, then node A
+      also tries to connect to node C. This feature can be turned off by
+      using the command-line flag -connect_all false, see the
+      erl(1) manual page in ERTS.

     
If a node goes down, all connections to that node are removed.
-      Calling erlang:disconnect_node(Node) will force disconnection
+      Calling erlang:disconnect_node(Node) forces disconnection
       of a node.

     
The list of (visible) nodes currently connected to is returned by
       nodes().

@@ -89,23 +91,24 @@ dilbert@uab

     
The Erlang Port Mapper Daemon epmd is automatically
       started at every host where an Erlang node is started. It is
       responsible for mapping the symbolic node names to machine
-      addresses. See epmd(1).

+      addresses. See the
+      epmd(1) manual page in ERTS.

   

 
   

     Hidden Nodes
     
In a distributed Erlang system, it is sometimes useful to
       connect to a node without also connecting to all other nodes.
-      An example could be some kind of O&M functionality used to
-      inspect the status of a system without disturbing it. For this
-      purpose, a hidden node may be used.

-    
A hidden node is a node started with the command line flag
+      An example is some kind of O&M functionality used to
+      inspect the status of a system, without disturbing it. For this
+      purpose, a hidden node can be used.

+    
A hidden node is a node started with the command-line flag
       -hidden. Connections between hidden nodes and other nodes
       are not transitive, they must be set up explicitly. Also, hidden
       nodes does not show up in the list of nodes returned by
       nodes(). Instead, nodes(hidden) or
       nodes(connected) must be used. This means, for example,
-      that the hidden node will not be added to the set of nodes that
+      that the hidden node is not added to the set of nodes that
       global is keeping track of.

     
This feature was added in Erlang 5.0/OTP R7.

   

@@ -114,9 +117,11 @@ dilbert@uab
C Nodes

A C node is a C program written to act as a hidden node in a distributed Erlang system. The library Erl_Interface - contains functions for this purpose. Refer to the documentation - for Erl_Interface and Interoperability Tutorial for more - information about C nodes.

+ contains functions for this purpose. For more information about + C nodes, see the + Erl_Interface application and + + Interoperability Tutorial..

@@ -125,7 +130,7 @@ dilbert@uab with each other. In a network of different Erlang nodes, it is built into the system at the lowest possible level. Each node has its own magic cookie, which is an Erlang atom.

-

When a nodes tries to connect to another node, the magic cookies +

When a node tries to connect to another node, the magic cookies are compared. If they do not match, the connected node rejects the connection.

At start-up, a node has a random atom assigned as its magic @@ -141,8 +146,8 @@ dilbert@uab the local node assume that all other nodes have the same cookie Cookie.

Thus, groups of users with identical cookie files get Erlang - nodes which can communicate freely and without interference from - the magic cookie system. Users who want run nodes on separate + nodes that can communicate freely and without interference from + the magic cookie system. Users who want to run nodes on separate file systems must make certain that their cookie files are identical on the different file systems.

For a node Node1 with magic cookie Cookie to be @@ -154,18 +159,24 @@ dilbert@uab

The default when a connection is established between two nodes, is to immediately connect all other visible nodes as well. This way, there is always a fully connected network. If there are - nodes with different cookies, this method might be inappropriate - and the command line flag -connect_all false must be set, - see erl(1).

+ nodes with different cookies, this method can be inappropriate + and the command-line flag -connect_all false must be set, + see the erl(1) + manual page in ERTS.

The magic cookie of the local node is retrieved by calling erlang:get_cookie().

Distribution BIFs -

Some useful BIFs for distributed programming, see - erlang(3) for more information:

+

Some useful BIFs for distributed programming + (for more information, see the + erlang(3) manual page in ERTS:

+ + BIF + Description + erlang:disconnect_node(Node) Forces the disconnection of a node. @@ -180,7 +191,9 @@ dilbert@uab monitor_node(Node, true|false) - Monitor the status of Node. A message{nodedown, Node} is received if the connection to it is lost. + Monitors the status of + Node. A message{nodedown, Node} is received + if the connection to it is lost. node() @@ -196,11 +209,16 @@ dilbert@uab nodes(Arg) - Depending on Arg, this function can return a list not only of visible nodes, but also hidden nodes and previously known nodes, etc. + Depending on Arg, + this function can return a list not only of visible nodes, + but also hidden nodes and previously known nodes, and so on. erlang:set_cookie(Node, Cookie) - Sets the magic cookie used when connecting to Node. If Node is the current node, Cookie will be used when connecting to all new nodes. + Sets the magic cookie used + when connecting to Node. If Node is the + current node, Cookie is used when connecting to + all new nodes. spawn[_link|_opt](Node, Fun) @@ -210,18 +228,24 @@ dilbert@uab spawn[_link|opt](Node, Module, FunctionName, Args) Creates a process at a remote node. - Distribution BIFs. + Distribution BIFs
- Distribution Command Line Flags -

Examples of command line flags used for distributed programming, - see erl(1) for more information:

+ Distribution Command-Line Flags +

Examples of command-line flags used for distributed programming + (for more information, see the erl(1) + manual page in ERTS:

+ + Command-Line Flag + Description + -connect_all false - Only explicit connection set-ups will be used. + Only explicit connection + set-ups are used. -hidden @@ -239,15 +263,19 @@ dilbert@uab -sname Name Makes a runtime system into a node, using short node names. - Distribution Command Line Flags. + Distribution Command-Line Flags
Distribution Modules

Examples of modules useful for distributed programming:

-

In Kernel:

+

In the Kernel application:

+ + Module + Description + global A global name registration facility. @@ -266,8 +294,12 @@ dilbert@uab Kernel Modules Useful For Distribution.
-

In STDLIB:

+

In the STDLIB application:

+ + Module + Description + slave Start and control of slave nodes. diff --git a/system/doc/reference_manual/errors.xml b/system/doc/reference_manual/errors.xml index dde6e68f4a..66ecf6aa94 100644 --- a/system/doc/reference_manual/errors.xml +++ b/system/doc/reference_manual/errors.xml @@ -4,7 +4,7 @@
- 20032013 + 20032015 Ericsson AB. All Rights Reserved. @@ -38,12 +38,12 @@ Run-time errors Generated errors -

A compile-time error, for example a syntax error, should not +

A compile-time error, for example a syntax error, does not cause much trouble as it is caught by the compiler.

A logical error is when a program does not behave as intended, - but does not crash. An example could be that nothing happens when + but does not crash. An example is that nothing happens when a button in a graphical user interface is clicked.

-

A run-time error is when a crash occurs. An example could be +

A run-time error is when a crash occurs. An example is when an operator is applied to arguments of the wrong type. The Erlang programming language has built-in features for handling of run-time errors.

@@ -54,23 +54,23 @@ of class error.

A generated error is when the code itself calls - exit/1 or throw/1. Note that emulated run-time + exit/1 or throw/1. Notice that emulated run-time errors are not denoted as generated errors here.

Generated errors are exceptions of classes exit and throw.

When a run-time error or generated error occurs in Erlang, - execution for the process which evaluated + execution for the process that evaluated the erroneous expression is stopped. This is referred to as a failure, that execution or evaluation fails, or that the process fails, - terminates or exits. Note that a process may + terminates, or exits. Notice that a process can terminate/exit for other reasons than a failure.

-

A process that terminates will emit an exit signal with +

A process that terminates emits an exit signal with an exit reason that says something about which error - has occurred. Normally, some information about the error will - be printed to the terminal.

+ has occurred. Normally, some information about the error is + printed to the terminal.

@@ -78,10 +78,12 @@

Exceptions are run-time errors or generated errors and are of three different classes, with different origins. The try expression - (appeared in Erlang 5.4/OTP-R10B) + (new in Erlang 5.4/OTP R10B) can distinguish between the different classes, whereas the catch - expression can not. They are described in the Expressions chapter.

+ expression cannot. They are described in + Expressions + .

Class @@ -89,7 +91,9 @@ error - Run-time error for example 1+a, or the process called erlang:error/1,2 (appeared in Erlang 5.4/OTP-R10B) + Run-time error, + for example, 1+a, or the process called + erlang:error/1,2 (new in Erlang 5.4/OTP R10B) exit @@ -102,11 +106,11 @@ Exception Classes.

An exception consists of its class, an exit reason - (the Exit Reason), - and a stack trace (that aids in finding the code location of + (see Exit Reason), + and a stack trace (which aids in finding the code location of the exception).

The stack trace can be retrieved using - erlang:get_stacktrace/0 (new in Erlang 5.4/OTP-R10B) + erlang:get_stacktrace/0 (new in Erlang 5.4/OTP R10B) from within a try expression, and is returned for exceptions of class error from a catch expression.

An exception of class error is also known as a run-time @@ -114,38 +118,38 @@

- Handling of Run-Time Errors in Erlang + Handling of Run-time Errors in Erlang
Error Handling Within Processes

It is possible to prevent run-time errors and other exceptions from causing the process to terminate by using catch or - try, see the Expressions chapter about - Catch - and Try.

+ try, see + Expressions about + catch + and try.

Error Handling Between Processes

Processes can monitor other processes and detect process terminations, see - the Processes - chapter.

+ Processes.

Exit Reasons -

When a run-time error occurs, - that is an exception of class error, - the exit reason is a tuple {Reason,Stack}. +

When a run-time error occurs, + that is an exception of class error. + The exit reason is a tuple {Reason,Stack}, where Reason is a term indicating the type of error:

Reason - Type of error + Type of Error badarg @@ -181,7 +185,7 @@ {badfun,F} - There is something wrong with a fun F. + Something is wrong with a fun F. {badarity,F} @@ -201,14 +205,17 @@ system_limit - A system limit has been reached. See Efficiency Guide for information about system limits. + A system limit has been reached. + See + Efficiency Guide for information about system limits. + - Exit Reasons. + Exit Reasons

Stack is the stack of function calls being evaluated when the error occurred, given as a list of tuples {Module,Name,Arity} with the most recent function call - first. The most recent function call tuple may in some + first. The most recent function call tuple can in some cases be {Module,Name,[Arg]}.

 diff --git a/system/doc/reference_manual/expressions.xml b/system/doc/reference_manual/expressions.xml index 62a344ad58..fd3cfabd3d 100644 --- a/system/doc/reference_manual/expressions.xml +++ b/system/doc/reference_manual/expressions.xml @@ -4,7 +4,7 @@
- 20032013 + 20032015 Ericsson AB. All Rights Reserved. @@ -28,13 +28,17 @@ expressions.xml
-

In this chapter, all valid Erlang expressions are listed. +

In this section, all valid Erlang expressions are listed. When writing Erlang programs, it is also allowed to use macro- and record expressions. However, these expressions are expanded during compilation and are in that sense not true Erlang expressions. Macro- and record expressions are covered in - separate chapters: Macros and - Records.

+ separate sections: +

+ +

Preprocessor

 +

Records

 +
Expression Evaluation @@ -48,15 +52,15 @@ Expr1 + Expr2 performed.

Many of the operators can only be applied to arguments of a certain type. For example, arithmetic operators can only be - applied to numbers. An argument of the wrong type will cause - a badarg run-time error.

+ applied to numbers. An argument of the wrong type causes + a badarg runtime error.

Terms

The simplest form of expression is a term, that is an integer, - float, atom, string, list, map or tuple. + float, atom, string, list, map, or tuple. The return value is the term itself.

@@ -65,9 +69,10 @@ Expr1 + Expr2

A variable is an expression. If a variable is bound to a value, the return value is this value. Unbound variables are only allowed in patterns.

-

Variables start with an uppercase letter or underscore (_) - and may contain alphanumeric characters, underscore and @. - Examples:

+

Variables start with an uppercase letter or underscore (_). + Variables can contain alphanumeric characters, underscore and @. +

+

Examples:

 X
 Name1
@@ -77,18 +82,20 @@ _
 _Height

Variables are bound to values using pattern matching. Erlang - uses single assignment, a variable can only be bound + uses single assignment, that is, a variable can only be bound once.

The anonymous variable is denoted by underscore (_) and can be used when a variable is required but its value can be - ignored. Example:

+ ignored.

+

Example:

 [H|_] = [1,2,3]
-

Variables starting with underscore (_), for example +

Variables starting with underscore (_), for example, _Height, are normal variables, not anonymous. They are - however ignored by the compiler in the sense that they will not - generate any warnings for unused variables. Example: The following - code

+ however ignored by the compiler in the sense that they do not + generate any warnings for unused variables.

+

Example:

+

The following code:

 member(_, []) ->
     [].
@@ -96,36 +103,37 @@ member(_, []) -> 
 member(Elem, []) ->
     [].
-

This will however cause a warning for an unused variable +

This causes a warning for an unused variable, Elem, if the code is compiled with the flag warn_unused_vars set. Instead, the code can be rewritten to:

 member(_Elem, []) ->
     [].
-

Note that since variables starting with an underscore are - not anonymous, this will match:

+

Notice that since variables starting with an underscore are + not anonymous, this matches:

 {_,_} = {1,2}
-

But this will fail:

+

But this fails:

 {_N,_N} = {1,2}

The scope for a variable is its function clause. Variables bound in a branch of an if, case, or receive expression must be bound in all branches - to have a value outside the expression, otherwise they - will be regarded as 'unsafe' outside the expression.

+ to have a value outside the expression. Otherwise they + are regarded as 'unsafe' outside the expression.

For the try expression introduced in - Erlang 5.4/OTP-R10B, variable scoping is limited so that + Erlang 5.4/OTP R10B, variable scoping is limited so that variables bound in the expression are always 'unsafe' outside - the expression. This will be improved.

+ the expression. This is to be improved.

Patterns -

A pattern has the same structure as a term but may contain - unbound variables. Example:

+

A pattern has the same structure as a term but can contain + unbound variables.

+

Example:

 Name1
 [H|T]
@@ -136,13 +144,13 @@ Name1
     

       Match Operator = in Patterns
       
If Pattern1 and Pattern2 are valid patterns,
-        then the following is also a valid pattern:

+        the following is also a valid pattern:

       
 Pattern1 = Pattern2

       
When matched against a term, both Pattern1 and
-        Pattern2 will be matched against the term. The idea
-        behind this feature is to avoid reconstruction of terms.
-        Example:

+        Pattern2 are  matched against the term. The idea
+        behind this feature is to avoid reconstruction of terms.

+       
Example:

       
 f({connect,From,To,Number,Options}, To) ->
     Signal = {connect,From,To,Number,Options},
@@ -163,16 +171,20 @@ f(Signal, To) ->
       
 f("prefix" ++ Str) -> ...

       
This is syntactic sugar for the equivalent, but harder to
-        read

+        read:

       
 f([$p,$r,$e,$f,$i,$x | Str]) -> ...

     

 
     

       Expressions in Patterns
-      
An arithmetic expression can be used within a pattern, if
-        it uses only numeric or bitwise operators, and if its value
-        can be evaluated to a constant at compile-time. Example:

+      
An arithmetic expression can be used within a pattern if
+        it meets both of the following two conditions:

+      
+        It uses only numeric or bitwise operators.
+        Its value can be evaluated to a constant when complied.
+      
+      
Example:

       
 case {Value, Result} of
     {?THRESHOLD+1, ok} -> ...

@@ -182,21 +194,21 @@ case {Value, Result} of
 
   

     Match
+    
The following matches Expr1, a pattern, against
+      Expr2:

     
 Expr1 = Expr2

-    
Matches Expr1, a pattern, against Expr2.
-      If the matching succeeds, any unbound variable in the pattern
+    
If the matching succeeds, any unbound variable in the pattern
       becomes bound and the value of Expr2 is returned.

-    
If the matching fails, a badmatch run-time error will
-      occur.

-    
Examples:

+    
If the matching fails, a badmatch run-time error occurs.

+    
Examples:

     
 1> {A, B} = {answer, 42}.
 {answer,42}
 2> A.
 answer
 3> {C, D} = [1, 2].
-** exception error: no match of right hand side value [1,2]

+** exception error: no match of right-hand side value [1,2]
@@ -210,27 +222,28 @@ ExprM:ExprF(Expr1,...,ExprN) ExprF must be an atom or an expression that evaluates to an atom. The function is said to be called by using the fully qualified function name. This is often referred - to as a remote or external function call. - Example:

+ to as a remote or external function call.

+

Example:

lists:keysearch(Name, 1, List)

In the second form of function calls, ExprF(Expr1,...,ExprN), ExprF must be an atom or evaluate to a fun.

-

If ExprF is an atom the function is said to be called by +

If ExprF is an atom, the function is said to be called by using the implicitly qualified function name. If the function ExprF is locally defined, it is called. - Alternatively if ExprF is explicitly imported from module - M, M:ExprF(Expr1,...,ExprN) is called. If + Alternatively, if ExprF is explicitly imported from the + M module, M:ExprF(Expr1,...,ExprN) is called. If ExprF is neither declared locally nor explicitly imported, ExprF must be the name of an automatically - imported BIF. Examples:

+ imported BIF.

+

Examples:

handle(Msg, State) spawn(m, init, []) -

Examples where ExprF is a fun:

+

Examples where ExprF is a fun:

Fun1 = fun(X) -> X+1 end Fun1(3) @@ -239,16 +252,15 @@ Fun1(3) fun lists:append/2([1,2], [3,4]) => [1,2,3,4] -

Note that when calling a local function, there is a difference - between using the implicitly or fully qualified function name, as - the latter always refers to the latest version of the module. See - Compilation and Code Loading.

- -

See also the chapter about - Function Evaluation.

+

Notice that when calling a local function, there is a difference + between using the implicitly or fully qualified function name. + The latter always refers to the latest version of the module. + See Compilation and Code Loading + and + Function Evaluation.

- Local Function Names Clashing With Auto-imported BIFs + Local Function Names Clashing With Auto-Imported BIFs

If a local function has the same name as an auto-imported BIF, the semantics is that implicitly qualified function calls are directed to the locally defined function, not to the BIF. To avoid @@ -260,9 +272,9 @@ fun lists:append/2([1,2], [3,4])

Before OTP R14A (ERTS version 5.8), an implicitly qualified function call to a function having the same name as an auto-imported BIF always resulted in the BIF being called. In - newer versions of the compiler the local function is instead - called. The change is there to avoid that future additions to the - set of auto-imported BIFs does not silently change the behavior + newer versions of the compiler, the local function is called instead. + This is to avoid that future additions to the + set of auto-imported BIFs do not silently change the behavior of old code.

However, to avoid that old (pre R14) code changed its @@ -272,8 +284,8 @@ fun lists:append/2([1,2], [3,4]) 5.8) and have an implicitly qualified call to that function in your code, you either need to explicitly remove the auto-import using a compiler directive, or replace the call with a fully - qualified function call, otherwise you will get a compilation - error. See example below:

+ qualified function call. Otherwise you get a compilation + error. See the following example:

-export([length/1,f/1]). @@ -290,9 +302,10 @@ f(X) when erlang:length(X) > 3 -> %% Calls erlang:length/1, long.

The same logic applies to explicitly imported functions from - other modules as to locally defined functions. To both import a + other modules, as to locally defined functions. + It is not allowed to both import a function from another module and have the function declared in the - module at the same time is not allowed.

+ module at the same time:

-export([f/1]). @@ -310,10 +323,10 @@ f(X) -> length(X). %% mod:length/1 is called -

For auto-imported BIFs added to Erlang in release R14A and thereafter, +

For auto-imported BIFs added in Erlang/OTP R14A and thereafter, overriding the name with a local function or explicit import is always allowed. However, if the -compile({no_auto_import,[F/A]) - directive is not used, the compiler will issue a warning whenever + directive is not used, the compiler issues a warning whenever the function is called in the module using the implicitly qualified function name.

@@ -330,15 +343,16 @@ if BodyN end

The branches of an if-expression are scanned sequentially - until a guard sequence GuardSeq which evaluates to true is + until a guard sequence GuardSeq that evaluates to true is found. Then the corresponding Body (sequence of expressions separated by ',') is evaluated.

The return value of Body is the return value of the if expression.

-

If no guard sequence is true, an if_clause run-time error - will occur. If necessary, the guard expression true can be +

If no guard sequence is evaluated as true, + an if_clause run-time error + occurs. If necessary, the guard expression true can be used in the last branch, as that guard sequence is always true.

-

Example:

+

Example:

 is_greater_than(X, Y) ->
     if
@@ -367,8 +381,8 @@ end

The return value of Body is the return value of the case expression.

If there is no matching pattern with a true guard sequence, - a case_clause run-time error will occur.

-

Example:

+ a case_clause run-time error occurs.

+

Example:

 is_valid_signal(Signal) ->
     case Signal of
@@ -389,15 +403,15 @@ Expr1 ! Expr2

Sends the value of Expr2 as a message to the process specified by Expr1. The value of Expr2 is also the return value of the expression.

-

Expr1 must evaluate to a pid, a registered name (atom) or - a tuple {Name,Node}, where Name is an atom and - Node a node name, also an atom.

+

Expr1 must evaluate to a pid, a registered name (atom), or + a tuple {Name,Node}. Name is an atom and + Node is a node name, also an atom.

If Expr1 evaluates to a name, but this name is not - registered, a badarg run-time error will occur. + registered, a badarg run-time error occurs. Sending a message to a pid never fails, even if the pid identifies a non-existing process. - Distributed message sending, that is if Expr1 + Distributed message sending, that is, if Expr1 evaluates to a tuple {Name,Node} (or a pid located at another node), also never fails. @@ -420,14 +434,14 @@ end the second, and so on. If a match succeeds and the optional guard sequence GuardSeq is true, the corresponding Body is evaluated. The matching message is consumed, that - is removed from the mailbox, while any other messages in + is, removed from the mailbox, while any other messages in the mailbox remain unchanged.

The return value of Body is the return value of the receive expression.

-

receive never fails. Execution is suspended, possibly - indefinitely, until a message arrives that does match one of +

receive never fails. The execution is suspended, possibly + indefinitely, until a message arrives that matches one of the patterns and with a true guard sequence.

-

Example:

+

Example:

 wait_for_onhook() ->
     receive
@@ -438,7 +452,7 @@ wait_for_onhook() ->
             B ! {busy, self()},
             wait_for_onhook()
     end.
-

It is possible to augment the receive expression with a +

The receive expression can be augmented with a timeout:

 receive
@@ -451,14 +465,14 @@ after
     ExprT ->
         BodyT
 end
-

ExprT should evaluate to an integer. The highest allowed - value is 16#ffffffff, that is, the value must fit in 32 bits. +

ExprT is to evaluate to an integer. The highest allowed + value is 16#FFFFFFFF, that is, the value must fit in 32 bits. receive..after works exactly as receive, except that if no matching message has arrived within ExprT - milliseconds, then BodyT is evaluated instead and its - return value becomes the return value of the receive..after - expression.

-

Example:

+ milliseconds, then BodyT is evaluated instead. The + return value of BodyT then becomes the return value + of the receive..after expression.

+

Example:

 wait_for_onhook() ->
     receive
@@ -481,10 +495,10 @@ after
     ExprT ->
         BodyT
 end
-

This construction will not consume any messages, only suspend - execution in the process for ExprT milliseconds and can be +

This construction does not consume any messages, only suspends + execution in the process for ExprT milliseconds. This can be used to implement simple timers.

-

Example:

+

Example:

 timer() ->
     spawn(m, timer, [self()]).
@@ -498,12 +512,12 @@ timer(Pid) ->
     
There are two special cases for the timeout value ExprT:

     
       infinity
-      The process should wait indefinitely for a matching message
-       -- this is the same as not using a timeout. Can be
-       useful for timeout values that are calculated at run-time.
+      The process is to wait indefinitely for a matching message;
+       this is the same as not using a timeout. This can be
+       useful for timeout values that are calculated at runtime.
       0
       If there is no matching message in the mailbox, the timeout
-       will occur immediately.
+       occurs immediately.
@@ -518,39 +532,39 @@ Expr1 op Expr2 == - equal to + Equal to /= - not equal to + Not equal to =< - less than or equal to + Less than or equal to < - less than + Less than >= - greater than or equal to + Greater than or equal to > - greater than + Greater than =:= - exactly equal to + Exactly equal to =/= - exactly not equal to + Exactly not equal to Term Comparison Operators. -

The arguments may be of different data types. The following +

The arguments can be of different data types. The following order is defined:

 number < atom < reference < fun < port < pid < tuple < list < bit string
@@ -558,17 +572,18 @@ number < atom < reference < fun < port < pid < tuple < list size, two tuples with the same size are compared element by element.

When comparing an integer to a float, the term with the lesser - precision will be converted into the other term's type, unless the - operator is one of =:= or =/=. A float is more precise than + precision is converted into the type of the other term, unless the + operator is one of =:= or =/=. A float is more precise than an integer until all significant figures of the float are to the left of the decimal point. This happens when the float is larger/smaller than +/-9007199254740992.0. The conversion strategy is changed depending on the size of the float because otherwise comparison of large floats and integers would lose their transitivity.

-

Returns the Boolean value of the expression, true or - false.

-

Examples:

+

Term comparison operators return the Boolean value of the + expression, true or false.

+ +

Examples:

 1> 1==1.0.
 true
@@ -585,19 +600,19 @@ false
Expr1 op Expr2 - op + Operator Description - Argument type + Argument Type + - unary + - number + Unary + + Number - - unary - - number + Unary - + Number + @@ -607,62 +622,62 @@ Expr1 op Expr2 -   - number + Number *   - number + Number / - floating point division - number + Floating point division + Number bnot - unary bitwise not - integer + Unary bitwise NOT + Integer div - integer division - integer + Integer division + Integer rem - integer remainder of X/Y - integer + Integer remainder of X/Y + Integer band - bitwise and - integer + Bitwise AND + Integer bor - bitwise or - integer + Bitwise OR + Integer bxor - arithmetic bitwise xor - integer + Arithmetic bitwise XOR + Integer bsl - arithmetic bitshift left - integer + Arithmetic bitshift left + Integer bsr - bitshift right - integer + Bitshift right + Integer Arithmetic Operators.
-

Examples:

+

Examples:

 1> +1.
 1
@@ -697,28 +712,28 @@ Expr1 op Expr2
Expr1 op Expr2 - op + Operator Description not - unary logical not + Unary logical NOT and - logical and + Logical AND or - logical or + Logical OR xor - logical xor + Logical XOR Logical Operators.
-

Examples:

+

Examples:

 1> not true.
 false
@@ -737,28 +752,37 @@ true
     
 Expr1 orelse Expr2
 Expr1 andalso Expr2

-    
Expressions where Expr2 is evaluated only if
-      necessary. That is, Expr2 is evaluated only if Expr1
-      evaluates to false in an orelse expression, or only
-      if Expr1 evaluates to true in an andalso
-      expression. Returns either the value of Expr1 (that is,
+    
Expr2 is evaluated only if
+      necessary. That is, Expr2 is evaluated only if:

+    
+      
Expr1 evaluates to false in an
+      orelse expression.

+      
+    
+      
or

+    
+      
Expr1 evaluates to true in an
+      andalso expression.

+      
+    
+    
Returns either the value of Expr1 (that is,
       true or false) or the value of Expr2
-      (if Expr2 was evaluated).

+      (if Expr2 is evaluated).

 
-    
Example 1:

+    
Example 1:

     
 case A >= -1.0 andalso math:sqrt(A+1) > B of

-    
This will work even if A is less than -1.0,
+    
This works even if A is less than -1.0,
       since in that case, math:sqrt/1 is never evaluated.

-    
Example 2:

+    
Example 2:

     
 OnlyOne = is_atom(L) orelse
          (is_list(L) andalso length(L) == 1),

 
-    
From R13A, Expr2 is no longer required to evaluate to a
-    boolean value. As a consequence, andalso and orelse
+    
From Erlang/OTP R13A, Expr2 is no longer required to evaluate to a
+    Boolean value. As a consequence, andalso and orelse
     are now tail-recursive.  For instance, the following function is
-    tail-recursive in R13A and later:

+    tail-recursive in Erlang/OTP R13A and later:

 
     
 all(Pred, [Hd|Tail]) ->
@@ -774,11 +798,11 @@ Expr1 ++ Expr2
 Expr1 -- Expr2

     
The list concatenation operator ++ appends its second
       argument to its first and returns the resulting list.

-    
The list subtraction operator -- produces a list which
-      is a copy of the first argument, subjected to the following
-      procedure: for each element in the second argument, the first
+    
The list subtraction operator -- produces a list that
+      is a copy of the first argument. The procedure is a follows:
+      for each element in the second argument, the first
       occurrence of this element (if any) is removed.

-    
Example:

+    
Example:

     
 1> [1,2,3]++[4,5].
 [1,2,3,4,5]
@@ -786,8 +810,8 @@ Expr1 -- Expr2

 [3,1,2]

The complexity of A -- B is - proportional to length(A)*length(B), meaning that it - will be very slow if both A and B are + proportional to length(A)*length(B). That is, it + becomes very slow if both A and B are long lists.

 @@ -802,7 +826,7 @@ Expr1 -- Expr2

#{ K => V }

- New maps may include multiple associations at construction by listing every + New maps can include multiple associations at construction by listing every association:

#{ K1 => V1, .., Kn => Vn } @@ -816,11 +840,11 @@ Expr1 -- Expr2

Keys and values are separated by the => arrow and associations are - separated by ,. + separated by a comma ,.

- Examples: + Examples:

M0 = #{}, % empty map @@ -829,14 +853,14 @@ M2 = #{1 => 2, b => b}, % multiple associations with literals M3 = #{k => {A,B}}, % single association with variables M4 = #{{"w", 1} => f()}. % compound key associated with an evaluated expression

- where, A and B are any expressions and M0 through M4 + Here, A and B are any expressions and M0 through M4 are the resulting map terms.

- If two matching keys are declared, the latter key will take precedence. + If two matching keys are declared, the latter key takes precedence.

- Example: + Example: 

@@ -846,54 +870,57 @@ M4 = #{{"w", 1} => f()}.  % compound key associated with an evaluated expression
 #{1 => b, 1.0 => a}

- The order in which the expressions constructing the keys and their - associated values are evaluated is not defined. The syntactic order of + The order in which the expressions constructing the keys (and their + associated values) are evaluated is not defined. The syntactic order of the key-value pairs in the construction is of no relevance, except in - the above mentioned case of two matching keys. + the recently mentioned case of two matching keys.

Updating Maps

- Updating a map has similar syntax as constructing it. + Updating a map has a similar syntax as constructing it.

- An expression defining the map to be updated is put in front of the expression - defining the keys to be updated and their respective values. + An expression defining the map to be updated, is put in front of the expression + defining the keys to be updated and their respective values:

M#{ K => V }

- where M is a term of type map and K and V are any expression. + Here M is a term of type map and K and V are any expression.

If key K does not match any existing key in the map, a new association - will be created from key K to value V. If key K matches - an existing key in map M its associated value will be replaced by the - new value V. In both cases the evaluated map expression will return a new map. + is created from key K to value V. +

+

If key K matches an existing key in map M, + its associated value + is replaced by the new value V. In both cases, the evaluated map expression + returns a new map.

- If M is not of type map an exception of type badmap is thrown. + If M is not of type map, an exception of type badmap is thrown.

- To only update an existing value, the following syntax is used, + To only update an existing value, the following syntax is used:

M#{ K := V }

- where M is an term of type map, V is an expression and K - is an expression which evaluates to an existing key in M. + Here M is a term of type map, V is an expression and K + is an expression that evaluates to an existing key in M.

- If key K does not match any existing keys in map M an exception - of type badarg will be triggered at runtime. If a matching key K - is present in map M its associated value will be replaced by the new - value V and the evaluated map expression returns a new map. + If key K does not match any existing keys in map M, an exception + of type badarg is triggered at runtime. If a matching key K + is present in map M, its associated value is replaced by the new + value V, and the evaluated map expression returns a new map.

- If M is not of type map an exception of type badmap is thrown. + If M is not of type map, an exception of type badmap is thrown.

- Examples: + Examples:

M0 = #{}, @@ -902,10 +929,10 @@ M2 = M1#{a => 1, b => 2}, M3 = M2#{"function" => fun() -> f() end}, M4 = M3#{a := 2, b := 3}. % 'a' and 'b' was added in `M1` and `M2`.

- where M0 is any map. It follows that M1 .. M4 are maps as well. + Here M0 is any map. It follows that M1 .. M4 are maps as well.

- More Examples: + More Examples: 

 1> M = #{1 => a}.
@@ -921,83 +948,84 @@ M4 = M3#{a := 2, b := 3}.  % 'a' and 'b' was added in `M1` and `M2`.
 		  As in construction, the order in which the key and value expressions
 		  are evaluated is not defined. The
 		  syntactic order of the key-value pairs in the update is of no
-		  relevance, except in the case where two keys match, in which
-		  case the latter value is used.
+		  relevance, except in the case where two keys match.
+		  In that case, the latter value is used.
Maps in Patterns

- Matching of key-value associations from maps is done in the following way: + Matching of key-value associations from maps is done as follows:

#{ K := V } = M

- where M is any map. The key K has to be an expression with bound - variables or a literals, and V can be any pattern with either bound or + Here M is any map. The key K must be an expression with bound + variables or literals. V can be any pattern with either bound or unbound variables.

- If the variable V is unbound, it will be bound to the value associated - with the key K, which has to exist in the map M. If the variable - V is bound, it has to match the value associated with K in M. + If the variable V is unbound, it becomes bound to the value associated + with the key K, which must exist in the map M. If the variable + V is bound, it must match the value associated with K in M.

-

Example:

- +

Example:

+
 1> M = #{"tuple" => {1,2}}.
 #{"tuple" => {1,2}}
 2> #{"tuple" := {1,B}} = M.
 #{"tuple" => {1,2}}
 3> B.
-2.
+2.

- This will bind variable B to integer 2. + This binds variable B to integer 2.

- Similarly, multiple values from the map may be matched: + Similarly, multiple values from the map can be matched:

#{ K1 := V1, .., Kn := Vn } = M

- where keys K1 .. Kn are any expressions with literals or bound variables. If all - keys exist in map M all variables in V1 .. Vn will be matched to the + Here keys K1 .. Kn are any expressions with literals or bound variables. If all + keys exist in map M, all variables in V1 .. Vn is matched to the associated values of their respective keys.

- If the matching conditions are not met, the match will fail, either with + If the matching conditions are not met, the match fails, either with:

- - a badmatch exception, if used in the context of the matching operator - as in the example, +

A badmatch exception.

+

This is if it is used in the context of the matching operator + as in the example.

 - - or resulting in the next clause being tested in function heads and - case expressions. +

Or resulting in the next clause being tested in function heads and + case expressions.

Matching in maps only allows for := as delimiters of associations. +

+

The order in which keys are declared in matching has no relevance.

- Duplicate keys are allowed in matching and will match each pattern associated - to the keys. + Duplicate keys are allowed in matching and match each pattern associated + to the keys:

#{ K := V1, K := V2 } = M

- Matching an expression against an empty map literal will match its type but - no variables will be bound: + Matching an expression against an empty map literal, matches its type but + no variables are bound:

#{} = Expr

- This expression will match if the expression Expr is of type map, otherwise - it will fail with an exception badmatch. + This expression matches if the expression Expr is of type map, otherwise + it fails with an exception badmatch.

- Matching syntax: Example with literals in function heads + Matching Syntax

- Matching of literals as keys are allowed in function heads. + Matching of literals as keys are allowed in function heads:

%% only start if not_started @@ -1014,17 +1042,19 @@ handle_call(change, From, #{ state := start } = S) ->
Maps in Guards

- Maps are allowed in guards as long as all sub-expressions are valid guard expressions. + Maps are allowed in guards as long as all subexpressions are valid guard expressions.

- Two guard BIFs handles maps: + Two guard BIFs handle maps:

is_map/1 + in the erlang module map_size/1 + in the erlang module
@@ -1044,29 +1074,34 @@ Ei = Value | Value/TypeSpecifierList | Value:Size/TypeSpecifierList

Used in a bit string construction, Value is an expression - which should evaluate to an integer, float or bit string. If the - expression is something else than a single literal or variable, it - should be enclosed in parenthesis.

+ that is to evaluate to an integer, float, or bit string. If the + expression is not a single literal or variable, it + is to be enclosed in parenthesis.

Used in a bit string matching, Value must be a variable, - or an integer, float or string.

+ or an integer, float, or string.

-

Note that, for example, using a string literal as in +

Notice that, for example, using a string literal as in >]]> is syntactic sugar for >]]>.

Used in a bit string construction, Size is an expression - which should evaluate to an integer.

+ that is to evaluate to an integer.

-

Used in a bit string matching, Size must be an integer or a +

Used in a bit string matching, Size must be an integer, or a variable bound to an integer.

The value of Size specifies the size of the segment in units (see below). The default value depends on the type (see - below). For integer it is 8, for - float it is 64, for binary and bitstring it is - the whole binary or bit string. In matching, this default value is only - valid for the very last element. All other bit string or binary + below):

+ + For integer it is 8. + For float it is 64. + For binary and bitstring it is + the whole binary or bit string. + +

In matching, this default value is only + valid for the last element. All other bit string or binary elements in the matching must have a size specification.

For the utf8, utf16, and utf32 types, @@ -1090,7 +1125,7 @@ Ei = Value | The default is unsigned. Endianness= big | little | native - Native-endian means that the endianness will be resolved at load + Native-endian means that the endianness is resolved at load time to be either big-endian or little-endian, depending on what is native for the CPU that the Erlang machine is run on. Endianness only matters when the Type is either integer, @@ -1099,7 +1134,7 @@ Ei = Value | Unit= unit:IntegerLiteral The allowed range is 1..256. Defaults to 1 for integer, - float and bitstring, and to 8 for binary. + float, and bitstring, and to 8 for binary. No unit specifier must be given for the types utf8, utf16, and utf32. @@ -1110,8 +1145,8 @@ Ei = Value |

When constructing binaries, if the size N of an integer segment is too small to contain the given integer, the most significant - bits of the integer will be silently discarded and only the N least - significant bits will be put into the binary.

+ bits of the integer are silently discarded and only the N least + significant bits are put into the binary.

The types utf8, utf16, and utf32 specifies encoding/decoding of the Unicode Transformation Formats UTF-8, UTF-16, @@ -1120,39 +1155,39 @@ Ei = Value |

When constructing a segment of a utf type, Value must be an integer in the range 0..16#D7FF or 16#E000....16#10FFFF. Construction - will fail with a badarg exception if Value is + fails with a badarg exception if Value is outside the allowed ranges. The size of the resulting binary - segment depends on the type and/or Value. For utf8, - Value will be encoded in 1 through 4 bytes. For - utf16, Value will be encoded in 2 or 4 - bytes. Finally, for utf32, Value will always be - encoded in 4 bytes.

+ segment depends on the type or Value, or both:

+ + For utf8, Value is encoded in 1-4 bytes. + For utf16, Value is encoded in 2 or 4 bytes. + For utf32, Value is always be encoded in 4 bytes. + -

When constructing, a literal string may be given followed +

When constructing, a literal string can be given followed by one of the UTF types, for example: >]]> - which is syntatic sugar for + which is syntactic sugar for >]]>.

-

A successful match of a segment of a utf type results +

A successful match of a segment of a utf type, results in an integer in the range 0..16#D7FF or 16#E000..16#10FFFF. - The match will fail if returned value - would fall outside those ranges.

+ The match fails if the returned value falls outside those ranges.

-

A segment of type utf8 will match 1 to 4 bytes in the binary, +

A segment of type utf8 matches 1-4 bytes in the binary, if the binary at the match position contains a valid UTF-8 sequence. (See RFC-3629 or the Unicode standard.)

-

A segment of type utf16 may match 2 or 4 bytes in the binary. - The match will fail if the binary at the match position does not contain +

A segment of type utf16 can match 2 or 4 bytes in the binary. + The match fails if the binary at the match position does not contain a legal UTF-16 encoding of a Unicode code point. (See RFC-2781 or the Unicode standard.)

-

A segment of type utf32 may match 4 bytes in the binary in the - same way as an integer segment matching 32 bits. - The match will fail if the resulting integer is outside the legal ranges +

A segment of type utf32 can match 4 bytes in the binary in the + same way as an integer segment matches 32 bits. + The match fails if the resulting integer is outside the legal ranges mentioned above.

-

Examples:

+

Examples:

 1> Bin1 = <<1,17,42>>.
 <<1,17,42>>
@@ -1181,11 +1216,13 @@ Ei = Value |
 13> <<1024/utf8>>.
 <<208,128>>
-

Note that bit string patterns cannot be nested.

-

Note also that ">]]>" is interpreted as +

Notice that bit string patterns cannot be nested.

+

Notice also that ">]]>" is interpreted as ">]]>" which is a syntax error. The correct way is to write a space after '=': ">]]>.

-

More examples can be found in Programming Examples.

+

More examples are provided in + + Programming Examples.

@@ -1200,16 +1237,16 @@ fun BodyK end

A fun expression begins with the keyword fun and ends - with the keyword end. Between them should be a function + with the keyword end. Between them is to be a function declaration, similar to a regular function declaration, - except that the function name is optional and should be a variable if + except that the function name is optional and is to be a variable, if any.

Variables in a fun head shadow the function name and both shadow - variables in the function clause surrounding the fun expression, and - variables bound in a fun body are local to the fun body.

+ variables in the function clause surrounding the fun expression. + Variables bound in a fun body are local to the fun body.

The return value of the expression is the resulting fun.

-

Examples:

+

Examples:

 1> Fun1 = fun (X) -> X+1 end.
 #Fun<erl_eval.6.39074546>
@@ -1232,15 +1269,17 @@ fun Module:Name/Arity
syntactic sugar for:

 fun (Arg1,...,ArgN) -> Name(Arg1,...,ArgN) end
-

In Module:Name/Arity, Module and Name are atoms - and Arity is an integer. Starting from the R15 release, - Module, Name, and Arity may also be variables. - A fun defined in this way will refer to the function Name +

In Module:Name/Arity, Module, and Name are atoms + and Arity is an integer. Starting from Erlang/OTP R15, + Module, Name, and Arity can also be variables. + A fun defined in this way refers to the function Name with arity Arity in the latest version of module - Module. A fun defined in this way will not be dependent on - the code for module in which it is defined. + Module. A fun defined in this way is not dependent on + the code for the module in which it is defined.

-

More examples can be found in Programming Examples.

+

More examples are provided in + + Programming Examples.

@@ -1250,23 +1289,26 @@ fun (Arg1,...,ArgN) -> Name(Arg1,...,ArgN) end catch Expr

Returns the value of Expr unless an exception occurs during the evaluation. In that case, the exception is - caught. For exceptions of class error, - that is run-time errors: {'EXIT',{Reason,Stack}} - is returned. For exceptions of class exit, that is - the code called exit(Term): {'EXIT',Term} is returned. - For exceptions of class throw, that is - the code called throw(Term): Term is returned.

+ caught.

+

For exceptions of class error, that is, + run-time errors, + {'EXIT',{Reason,Stack}} is returned.

+

For exceptions of class exit, that is, + the code called exit(Term), + {'EXIT',Term} is returned.

+

For exceptions of class throw, that is + the code called throw(Term), + Term is returned.

Reason depends on the type of error that occurred, and Stack is the stack of recent function calls, see - Errors and Error Handling.

-

Examples:

-

+ Exit Reasons.

+

Examples:

 1> catch 1+2.
 3
 2> catch 1+a.
 {'EXIT',{badarith,[...]}}
-

Note that catch has low precedence and catch +

Notice that catch has low precedence and catch subexpressions often needs to be enclosed in a block expression or in parenthesis:

@@ -1275,13 +1317,14 @@ catch Expr
 4> A = (catch 1+2).
 3

The BIF throw(Any) can be used for non-local return from - a function. It must be evaluated within a catch, which will - return the value Any. Example:

+ a function. It must be evaluated within a catch, which + returns the value Any.

+

Example:

 5> catch throw(hello).
 hello

If throw/1 is not evaluated within a catch, a - nocatch run-time error will occur.

+ nocatch run-time error occurs.

@@ -1297,14 +1340,17 @@ catch end

This is an enhancement of catch that appeared in - Erlang 5.4/OTP-R10B. It gives the possibility do distinguish - between different exception classes, and to choose to handle only - the desired ones, passing the others on to an enclosing - try or catch or to default error handling.

-

Note that although the keyword catch is used in + Erlang 5.4/OTP R10B. It gives the possibility to:

+ + Distinguish between different exception classes. + Choose to handle only the desired ones. + Passing the others on to an enclosing + try or catch, or to default error handling. + +

Notice that although the keyword catch is used in the try expression, there is not a catch expression within the try expression.

-

Returns the value of Exprs (a sequence of expressions +

It returns the value of Exprs (a sequence of expressions Expr1, ..., ExprN) unless an exception occurs during the evaluation. In that case the exception is caught and the patterns ExceptionPattern with the right exception @@ -1318,7 +1364,7 @@ end Class with a true guard sequence, the exception is passed on as if Exprs had not been enclosed in a try expression.

-

If an exception occurs during evaluation of ExceptionBody +

If an exception occurs during evaluation of ExceptionBody, it is not caught.

The try expression can have an of section: @@ -1341,7 +1387,7 @@ end the patterns Pattern are sequentially matched against the result in the same way as for a case expression, except that if - the matching fails, a try_clause run-time error will occur.

+ the matching fails, a try_clause run-time error occurs.

An exception occurring during the evaluation of Body is not caught.

The try expression can also be augmented with an @@ -1364,7 +1410,7 @@ after AfterBody end

AfterBody is evaluated after either Body or - ExceptionBody no matter which one. The evaluated value of + ExceptionBody, no matter which one. The evaluated value of AfterBody is lost; the return value of the try expression is the same with an after section as without.

Even if an exception occurs during evaluation of Body or @@ -1373,13 +1419,13 @@ end evaluated, so the exception from the try expression is the same with an after section as without.

If an exception occurs during evaluation of AfterBody - itself it is not caught, so if AfterBody is evaluated after - an exception in Exprs, Body or ExceptionBody, + itself, it is not caught. So if AfterBody is evaluated after + an exception in Exprs, Body, or ExceptionBody, that exception is lost and masked by the exception in AfterBody.

-

The of, catch and after sections are all +

The of, catch, and after sections are all optional, as long as there is at least a catch or an - after section, so the following are valid try + after section. So the following are valid try expressions:

try Exprs of @@ -1398,9 +1444,9 @@ after end try Exprs after AfterBody end -

Example of using after, this code will close the file +

Next is an example of using after. This closes the file, even in the event of exceptions in file:read/2 or in - binary_to_term/1, and exceptions will be the same as + binary_to_term/1. The exceptions are the same as without the try...after...end expression:

termize_file(Name) -> @@ -1411,7 +1457,7 @@ termize_file(Name) -> after file:close(F) end. -

Example: Using try to emulate catch Expr.

+

Next is an example of using try to emulate catch Expr:

try Expr catch @@ -1427,7 +1473,7 @@ end (Expr)

Parenthesized expressions are useful to override operator precedences, - for example in arithmetic expressions:

+ for example, in arithmetic expressions:

 1> 1 + 2 * 3.
 7
@@ -1451,7 +1497,7 @@ end
List Comprehensions -

List comprehensions are a feature of many modern functional +

List comprehensions is a feature of many modern functional programming languages. Subject to certain rules, they provide a succinct notation for generating elements in a list.

List comprehensions are analogous to set comprehensions in @@ -1461,32 +1507,34 @@ end

List comprehensions are written with the following syntax:

 [Expr || Qualifier1,...,QualifierN]
-

Expr is an arbitrary expression, and each +

Here, Expr is an arbitrary expression, and each Qualifier is either a generator or a filter.

A generator is written as:

  .

-ListExpr must be an expression which evaluates to a +ListExpr must be an expression, which evaluates to a list of terms. A bit string generator is written as:

  .

-BitStringExpr must be an expression which evaluates to a +BitStringExpr must be an expression, which evaluates to a bitstring. - A filter is an expression which evaluates to + A filter is an expression, which evaluates to true or false. -

The variables in the generator patterns shadow variables in the function - clause surrounding the list comprehensions.

A list comprehension +

The variables in the generator patterns, shadow variables in the function + clause, surrounding the list comprehensions.

A list comprehension returns a list, where the elements are the result of evaluating Expr for each combination of generator list elements and bit string generator - elements for which all filters are true.

Example:

+ elements, for which all filters are true.

+

Example:

 1> [X*2 || X <- [1,2,3]].
 [2,4,6]
-

More examples can be found in Programming Examples.

- +

More examples are provoded in + + Programming Examples.

@@ -1500,34 +1548,35 @@ end the following syntax:

 << BitString || Qualifier1,...,QualifierN >>
-

BitString is a bit string expression, and each +

Here, BitString is a bit string expression and each Qualifier is either a generator, a bit string generator or a filter.

A generator is written as:

  .

- ListExpr must be an expression which evaluates to a + ListExpr must be an expression that evaluates to a list of terms. A bit string generator is written as:

  .

-BitStringExpr must be an expression which evaluates to a +BitStringExpr must be an expression that evaluates to a bitstring. - A filter is an expression which evaluates to + A filter is an expression that evaluates to true or false. -

The variables in the generator patterns shadow variables in - the function clause surrounding the bit string comprehensions.

+

The variables in the generator patterns, shadow variables in + the function clause, surrounding the bit string comprehensions.

A bit string comprehension returns a bit string, which is created by concatenating the results of evaluating BitString - for each combination of bit string generator elements for which all + for each combination of bit string generator elements, for which all filters are true.

-

-

Example:

+

Example:

-1> << << (X*2) >> || 
+1> << << (X*2) >> ||
 <<X>> <= << 1,2,3 >> >>.
 <<2,4,6>>
-

More examples can be found in Programming Examples.

+

More examples are provided in + + Programming Examples.

@@ -1536,27 +1585,27 @@ end

A guard sequence is a sequence of guards, separated by semicolon (;). The guard sequence is true if at least one of - the guards is true. (The remaining guards, if any, will not be - evaluated.)

-Guard1;...;GuardK

+ the guards is true. (The remaining guards, if any, are not + evaluated.)

+

Guard1;...;GuardK

A guard is a sequence of guard expressions, separated by comma (,). The guard is true if all guard expressions - evaluate to true.

-GuardExpr1,...,GuardExprN

+ evaluate to true.

+

GuardExpr1,...,GuardExprN

The set of valid guard expressions (sometimes called guard tests) is a subset of the set of valid Erlang expressions. The reason for restricting the set of valid expressions is that evaluation of a guard expression must be guaranteed to be free - of side effects. Valid guard expressions are:

+ of side effects. Valid guard expressions are the following:

- the atom true, - other constants (terms and bound variables), all regarded - as false, - calls to the BIFs specified below, - term comparisons, - arithmetic expressions, - boolean expressions, and - short-circuit expressions (andalso/orelse). + The atom true + Other constants (terms and bound variables), all regarded + as false + Calls to the BIFs specified in table Type Test BIFs + Term comparisons + Arithmetic expressions + Boolean expressions + Short-circuit expressions (andalso/orelse) @@ -1610,13 +1659,13 @@ end is_tuple/1 - Type Test BIFs. + Type Test BIFs
-

Note that most type test BIFs have older equivalents, without +

Notice that most type test BIFs have older equivalents, without the is_ prefix. These old BIFs are retained for backwards - compatibility only and should not be used in new code. They are + compatibility only and are not to be used in new code. They are also only allowed at top level. For example, they are not allowed - in boolean expressions in guards.

+ in Boolean expressions in guards.

abs(Number) @@ -1666,14 +1715,14 @@ end tuple_size(Tuple) - Other BIFs Allowed in Guard Expressions. + Other BIFs Allowed in Guard Expressions
-

If an arithmetic expression, a boolean expression, a +

If an arithmetic expression, a Boolean expression, a short-circuit expression, or a call to a guard BIF fails (because of invalid arguments), the entire guard fails. If the guard was part of a guard sequence, the next guard in the sequence (that is, - the guard following the next semicolon) will be evaluated.

+ the guard following the next semicolon) is evaluated.

@@ -1726,12 +1775,13 @@ end catch   - Operator Precedence. + Operator Precedence

When evaluating an expression, the operator with the highest priority is evaluated first. Operators with the same priority - are evaluated according to their associativity. Example: - The left associative arithmetic operators are evaluated left to + are evaluated according to their associativity.

+

Example:

+

The left associative arithmetic operators are evaluated left to right:

 6 + 5 * 4 - 3 / 2 evaluates to
diff --git a/system/doc/reference_manual/functions.xml b/system/doc/reference_manual/functions.xml
index 9498ef1402..8cf4da1b8b 100644
--- a/system/doc/reference_manual/functions.xml
+++ b/system/doc/reference_manual/functions.xml
@@ -4,7 +4,7 @@
 
   

     
-      20032013
+      20032015
       Ericsson AB. All Rights Reserved.
     
     
@@ -38,7 +38,7 @@
       clause body, separated by ->.

     
A clause head consists of the function name, an
       argument list, and an optional guard sequence
-      beginning with the keyword when.

+      beginning with the keyword when:

     
 Name(Pattern11,...,Pattern1N) [when GuardSeq1] ->
     Body1;
@@ -48,9 +48,9 @@ Name(PatternK1,...,PatternKN) [when GuardSeqK] ->
     
The function name is an atom. Each argument is a pattern.

     
The number of arguments N is the arity of
       the function. A function is uniquely defined by the module name,
-      function name and arity. That is, two functions with the same
+      function name, and arity. That is, two functions with the same
       name and in the same module, but with different arities are two
-      completely different functions.

+      different functions.

     
A function named f in the module m and with arity
       N is often denoted as m:f/N.

     
A clause body consists of a sequence of expressions
@@ -60,8 +60,8 @@ Expr1,
 ...,
 ExprN

     
Valid Erlang expressions and guard sequences are described in
-      Erlang Expressions.

-    
Example:

+      Expressions.

+    
Example:

     
 fact(N) when N>0 ->  % first clause head
     N * fact(N-1);   % first clause body
@@ -75,23 +75,23 @@ fact(0) ->           % second clause head
     Function Evaluation
     
When a function m:f/N is called, first the code for
       the function is located. If the function cannot be found, an
-      undef run-time error will occur. Note that the function
+      undef runtime error occurs. Notice that the function
       must be exported to be visible outside the module it is defined
       in.

     
If the function is found, the function clauses are scanned
-      sequentially until a clause is found that fulfills the following
-      two conditions:

+      sequentially until a clause is found that fulfills both of
+      the following two conditions:

     
-      the patterns in the clause head can be successfully
-       matched against the given arguments, and
-      the guard sequence, if any, is true.
+      The patterns in the clause head can be successfully
+       matched against the given arguments.
+      The guard sequence, if any, is true.
     
     
If such a clause cannot be found, a function_clause
-      run-time error will occur.

+      runtime error occurs.

     
If such a clause is found, the corresponding clause body is
       evaluated. That is, the expressions in the body are evaluated
       sequentially and the value of the last expression is returned.

-    
Example: Consider the function fact:

+    
Consider the function fact:

     
 -module(m).
 -export([fact/1]).
@@ -100,17 +100,17 @@ fact(N) when N>0 ->
     N * fact(N-1);
 fact(0) ->
     1.

-    
Assume we want to calculate factorial for 1:

+    
Assume that you want to calculate the factorial for 1:

     
 1> m:fact(1).

     
Evaluation starts at the first clause. The pattern N is
-      matched against the argument 1. The matching succeeds and
-      the guard (N>0) is true, thus N is bound to 1 and
+      matched against argument 1. The matching succeeds and
+      the guard (N>0) is true, thus N is bound to 1, and
       the corresponding body is evaluated:

     
 N * fact(N-1) => (N is bound to 1)
 1 * fact(0)

-    
Now fact(0) is called and the function clauses are
+    
Now, fact(0) is called, and the function clauses are
       scanned sequentially again. First, the pattern N is
       matched against 0. The matching succeeds, but the guard
       (N>0) is false. Second, the pattern 0 is matched against
@@ -121,48 +121,51 @@ fact(0) ->
 1

     
Evaluation has succeed and m:fact(1) returns 1.

     
If m:fact/1 is called with a negative number as
-      argument, no clause head will match. A function_clause
-      run-time error will occur.

+      argument, no clause head matches. A function_clause
+      runtime error occurs.
Tail recursion

If the last expression of a function body is a function call, - a tail recursive call is done so that no system - resources for example call stack are consumed. This means - that an infinite loop can be done if it uses tail recursive + a tail recursive call is done. + This is to ensure that no system + resources, for example, call stack, are consumed. This means + that an infinite loop can be done if it uses tail-recursive calls.

-

Example:

+

Example:

 loop(N) ->
     io:format("~w~n", [N]),
     loop(N+1).
-

As a counter-example see the factorial example above - that is not tail recursive since a multiplication is done +

The earlier factorial example can act as a counter-example. + It is not tail-recursive, since a multiplication is done on the result of the recursive call to fact(N-1).

- Built-In Functions, BIFs -

Built-in functions, BIFs, are implemented in C code in - the runtime system and do things that are difficult or impossible - to implement in Erlang. Most of the built-in functions belong - to the module erlang but there are also built-in functions + Built-In Functions (BIFs) +

BIFs are implemented in C code in + the runtime system. BIFs do things that are difficult or impossible + to implement in Erlang. Most of the BIFs belong + to the module erlang but there are also BIFs belonging to a few other modules, for example lists and ets.

-

The most commonly used BIFs belonging to erlang are - auto-imported, they do not need to be prefixed with - the module name. Which BIFs are auto-imported is specified in - erlang(3). For example, standard type conversion BIFs like +

The most commonly used BIFs belonging to erlang(3) are + auto-imported. They do not need to be prefixed with + the module name. Which BIFs that are auto-imported is specified in the + erlang(3) module in ERTS. + For example, standard-type conversion BIFs like atom_to_list and BIFs allowed in guards can be called - without specifying the module name. Examples:

+ without specifying the module name.

+

Examples:

 1> tuple_size({a,b,c}).
 3
 2> atom_to_list('Erlang').
 "Erlang"
-

Note that normally it is the set of auto-imported built-in - functions that is referred to when talking about 'BIFs'.

+

Notice that it is normally the set of auto-imported BIFs + that are referred to when talking about 'BIFs'.

 diff --git a/system/doc/reference_manual/introduction.xml b/system/doc/reference_manual/introduction.xml index 36bec17825..ee8b82e60f 100644 --- a/system/doc/reference_manual/introduction.xml +++ b/system/doc/reference_manual/introduction.xml @@ -4,7 +4,7 @@
- 20032014 + 20032015 Ericsson AB. All Rights Reserved. @@ -28,20 +28,38 @@ introduction.xml
+ + +

This section is the Erlang reference manual. It describes the + Erlang programming language.

Purpose -

This reference manual describes the Erlang programming - language. The focus is on the language itself, not - the implementation. The language constructs are described in - text and with examples rather than formally specified, with - the intention to make the manual more readable. - The manual is not intended as a tutorial.

-

Information about this implementation of Erlang can be found, for - example, in System Principles (starting and stopping, - boot scripts, code loading, error logging, creating target - systems), Efficiency Guide (memory consumption, system - limits) and ERTS User's Guide (crash dumps, drivers).

+

The focus of the Erlang reference manual is on the language itself, + not the implementation of it. The language constructs are described in + text and with examples rather than formally specified. This is + to make the manual more readable. + The Erlang reference manual is not intended as a tutorial.

+

Information about implementation of Erlang can, for example, be found, + in the following:

+ +

+ System Principles

+

Starting and stopping, boot scripts, code loading, + + error logging, + + creating target systems

+ +

+ Efficiency Guide

+

Memory consumption, system limits

+ +

ERTS User's Guide

+

Crash dumps, + drivers

+ +
@@ -53,13 +71,13 @@
Document Conventions -

In the document, the following terminology is used:

+

In this section, the following terminology is used:

A sequence is one or more items. For example, a clause body consists of a sequence of expressions. This means that there must be at least one expression. A list is any number of items. For example, - an argument list can consist of zero, one or more arguments. + an argument list can consist of zero, one, or more arguments.

If a feature has been added recently, in Erlang 5.0/OTP R7 or later, this is mentioned in the text.

@@ -68,15 +86,16 @@
Complete List of BIFs

For a complete list of BIFs, their arguments and return values, - refer to erlang(3).

+ see erlang(3) + manual page in ERTS.

Reserved Words

The following are reserved words in Erlang:

-

after and andalso band begin bnot bor bsl bsr bxor case catch +

after and andalso band begin bnot bor bsl bsr bxor case catch cond div end fun if let not of or orelse receive rem try - when xor

+ when xor

diff --git a/system/doc/reference_manual/macros.xml b/system/doc/reference_manual/macros.xml index 9fd0b0f287..01994aae5e 100644 --- a/system/doc/reference_manual/macros.xml +++ b/system/doc/reference_manual/macros.xml @@ -4,7 +4,7 @@
- 20032013 + 20032015 Ericsson AB. All Rights Reserved. @@ -21,7 +21,7 @@ - The Preprocessor + Preprocessor @@ -31,17 +31,17 @@
File Inclusion -

A file can be included in the following way:

+

A file can be included as follows:

 -include(File).
 -include_lib(File).
-

File, a string, should point out a file. The contents of - this file are included as-is, at the position of the directive.

+

File, a string, is to point out a file. The contents of + this file are included as is, at the position of the directive.

Include files are typically used for record and macro definitions that are shared by several modules. It is - recommended that the file name extension .hrl be used - for include files.

-

File may start with a path component $VAR, for + recommended to use the file name extension .hrl for + include files.

+

File can start with a path component $VAR, for some string VAR. If that is the case, the value of the environment variable VAR as returned by os:getenv(VAR) is substituted for $VAR. If @@ -49,21 +49,29 @@ as is.

If the filename File is absolute (possibly after variable substitution), the include file with that name is - included. Otherwise, the specified file is searched for in - the current working directory, in the same directory as - the module being compiled, and in the directories given by - the include option, in that order. - See erlc(1) and compile(3) for details.

-

Examples:

+ included. Otherwise, the specified file is searched for + in the following directories, and in this order:

+ + The current working directory + The directory where the module is being compiled + The directories given by the include option + +

For details, see the + erlc(1) manual page + in ERTS and + compile(3) + manual page in Compiler.

+

Examples:

 -include("my_records.hrl").
 -include("incdir/my_records.hrl").
 -include("/home/user/proj/my_records.hrl").
 -include("$PROJ_ROOT/my_records.hrl").
-

include_lib is similar to include, but should not +

include_lib is similar to include, but is not to point out an absolute file. Instead, the first path component (possibly after variable substitution) is assumed to be - the name of an application. Example:

+ the name of an application.

+

Example:

 -include_lib("kernel/include/file.hrl").

The code server uses code:lib_dir(kernel) to find @@ -74,7 +82,7 @@

Defining and Using Macros -

A macro is defined the following way:

+

A macro is defined as follows:

-define(Const, Replacement). -define(Func(Var1,...,VarN), Replacement). @@ -83,33 +91,34 @@ come before any usage of the macro.

If a macro is used in several modules, it is recommended that the macro definition is placed in an include file.

-

A macro is used the following way:

+

A macro is used as follows:

?Const ?Func(Arg1,...,ArgN)

Macros are expanded during compilation. A simple macro - ?Const will be replaced with Replacement. - Example:

+ ?Const is replaced with Replacement.

+

Example:

-define(TIMEOUT, 200). ... call(Request) -> server:call(refserver, Request, ?TIMEOUT). -

This will be expanded to:

+

This is expanded to:

call(Request) -> server:call(refserver, Request, 200). -

A macro ?Func(Arg1,...,ArgN) will be replaced with +

A macro ?Func(Arg1,...,ArgN) is replaced with Replacement, where all occurrences of a variable Var from the macro definition are replaced with the corresponding - argument Arg. Example:

+ argument Arg.

+

Example:

-define(MACRO1(X, Y), {a, X, b, Y}). ... bar(X) -> ?MACRO1(a, b), ?MACRO1(X, 123) -

This will be expanded to:

+

This is expanded to:

bar(X) -> {a,a,b,b}, @@ -154,7 +163,7 @@ bar(X) -> -define(F0(), c). -define(F1(A), A). -define(C, m:f). -

the following will not work:

+

the following does not work:

f0() -> ?F0. % No, an empty list of arguments expected. @@ -165,7 +174,7 @@ f1(A) -> f() -> ?C(). -

will expand to

+

is expanded to

f() -> m:f(). @@ -185,7 +194,7 @@ f() -> defined. -else. Only allowed after an ifdef or ifndef - directive. If that condition was false, the lines following + directive. If that condition is false, the lines following else are evaluated instead. -endif. Specifies the end of an ifdef or ifndef @@ -194,7 +203,7 @@ f() ->

The macro directives cannot be used inside functions.

 -

Example:

+

Example:

-module(m). ... @@ -206,7 +215,7 @@ f() -> -endif. ... -

When trace output is desired, debug should be defined +

When trace output is desired, debug is to be defined when the module m is compiled:

 % erlc -Ddebug m.erl
@@ -215,18 +224,18 @@ or
 
 1> c(m, {d, debug}).
 {ok,m}
-

?LOG(Arg) will then expand to a call to io:format/2 +

?LOG(Arg) is then expanded to a call to io:format/2 and provide the user with some simple trace output.

Stringifying Macro Arguments

The construction ??Arg, where Arg is a macro - argument, will be expanded to a string containing the tokens of + argument, is expanded to a string containing the tokens of the argument. This is similar to the #arg stringifying construction in C.

The feature was added in Erlang 5.0/OTP R7.

-

Example:

+

Example:

-define(TESTCALL(Call), io:format("Call ~s: ~w~n", [??Call, Call])). @@ -236,7 +245,7 @@ or io:format("Call ~s: ~w~n",["myfunction ( 1 , 2 )",myfunction(1,2)]), io:format("Call ~s: ~w~n",["you : function ( 2 , 1 )",you:function(2,1)]). -

That is, a trace output with both the function called and +

That is, a trace output, with both the function called and the resulting value.

diff --git a/system/doc/reference_manual/modules.xml b/system/doc/reference_manual/modules.xml index 5cb0c11371..39c739a146 100644 --- a/system/doc/reference_manual/modules.xml +++ b/system/doc/reference_manual/modules.xml @@ -4,7 +4,7 @@
- 20032014 + 20032015 Ericsson AB. All Rights Reserved. @@ -33,7 +33,8 @@ Module Syntax

Erlang code is divided into modules. A module consists of a sequence of attributes and function declarations, each - terminated by period (.). Example:

+ terminated by period (.).

+

Example:

 -module(m).          % module attribute
 -export([fact/1]).   % module attribute
@@ -42,50 +43,52 @@ fact(N) when N>0 ->  % beginning of function declaration
     N * fact(N-1);   %  |
 fact(0) ->           %  |
     1.               % end of function declaration
-

See the Functions chapter - for a description of function declarations.

+

For a description of function declarations, see + Function Declaration Syntax.

Module Attributes

A module attribute defines a certain property of a - module. A module attribute consists of a tag and a value.

+ module.

+

A module attribute consists of a tag and a value:

 -Tag(Value).

Tag must be an atom, while Value must be a literal term. As a convenience in user-defined attributes, if the literal term Value has the syntax Name/Arity (where Name is an atom and Arity a positive integer), - the term Name/Arity will be translated to {Name,Arity}.

+ the term Name/Arity is translated to {Name,Arity}.

Any module attribute can be specified. The attributes are stored in the compiled code and can be retrieved by calling - Module:module_info(attributes) or by using - beam_lib(3).

+ Module:module_info(attributes), or by using the module + beam_lib(3) + in STDLIB.

-

There are several module attributes with predefined meanings, - some of which have arity two, but user-defined module +

Several module attributes have predefined meanings. + Some of them have arity two, but user-defined module attributes must have arity one.

Pre-Defined Module Attributes -

Pre-defined module attributes should be placed before any +

Pre-defined module attributes is to be placed before any function declaration.

-module(Module).

Module declaration, defining the name of the module. - The name Module, an atom, should be the same as - the file name minus the extension erl. Otherwise - code loading will + The name Module, an atom, is to be same as + the file name minus the extension .erl. Otherwise + code loading does not work as intended.

-

This attribute should be specified first and is the only - attribute which is mandatory.

+

This attribute is to be specified first and is the only + mandatory attribute.

 -export(Functions). -

Exported functions. Specifies which of the functions - defined within the module that are visible outside +

Exported functions. Specifies which of the functions, + defined within the module, that are visible from outside the module.

Functions is a list [Name1/Arity1, ..., NameN/ArityN], where each @@ -93,32 +96,37 @@ fact(0) -> % | -import(Module,Functions). -

Imported functions. Imported functions can be called - the same way as local functions, that is without any module +

Imported functions. Can be called + the same way as local functions, that is, without any module prefix.

Module, an atom, specifies which module to import functions from. Functions is a list similar as for - export above.

+ export.

 -compile(Options). -

Compiler options. Options, which is a single option - or a list of options, will be added to the option list when - compiling the module. See compile(3).

+

Compiler options. Options is a single option + or a list of options. + This attribute is added to the option list when + compiling the module. See the + compile(3) manual page in Compiler.

 -vsn(Vsn).

Module version. Vsn is any literal term and can be - retrieved using beam_lib:version/1, see - beam_lib(3).

+ retrieved using beam_lib:version/1, see the + beam_lib(3) + manual page in STDLIB.

If this attribute is not specified, the version defaults to the MD5 checksum of the module.

 -on_load(Function). -

Names a function that should be run automatically when a - module a loaded. See - code loading for more information.

+

This attribute names a function that is to be run + automatically when a + module is loaded. For more information, see + + Running a Function When a Module is Loaded.
@@ -130,9 +138,14 @@ fact(0) -> % | 
 -behaviour(Behaviour).

The atom Behaviour gives the name of the behaviour, - which can be a user defined behaviour or one of the OTP - standard behaviours gen_server, gen_fsm, - gen_event or supervisor.

+ which can be a user-defined behaviour or one of the following OTP + standard behaviours:

+ + gen_server + gen_fsm + gen_event + supervisor +

The spelling behavior is also accepted.

The callback functions of the module can be specified either directly by the exported function behaviour_info/1:

@@ -142,7 +155,7 @@ behaviour_info(callbacks) -> Callbacks. function:

 -callback Name(Arguments) -> Result.
-

where Arguments is a list of zero or more arguments. +

Here, Arguments is a list of zero or more arguments. The -callback attribute is to be preferred since the extra type information can be used by tools to produce documentation or find discrepancies.

@@ -153,7 +166,7 @@ behaviour_info(callbacks) -> Callbacks.
Record Definitions -

The same syntax as for module attributes is used by +

The same syntax as for module attributes is used for record definitions:

 -record(Record,Fields).
@@ -163,7 +176,7 @@ behaviour_info(callbacks) -> Callbacks.
- The Preprocessor + Preprocessor

The same syntax as for module attributes is used by the preprocessor, which supports file inclusion, macros, and conditional compilation:

@@ -171,7 +184,7 @@ behaviour_info(callbacks) -> Callbacks. -include("SomeFile.hrl"). -define(Macro,Replacement). -

Read more in The Preprocessor.

+

Read more in Preprocessor.

@@ -180,17 +193,17 @@ behaviour_info(callbacks) -> Callbacks. changing the pre-defined macros ?FILE and ?LINE:

 -file(File, Line).
-

This attribute is used by tools such as Yecc to inform the - compiler that the source program was generated by another tool - and indicates the correspondence of source files to lines of - the original user-written file from which the source program - was produced.

+

This attribute is used by tools, such as Yecc, to inform the + compiler that the source program is generated by another tool. + It also indicates the correspondence of source files to lines of + the original user-written file, from which the source program + is produced.

Types and function specifications

A similar syntax as for module attributes is used for - specifying types and function specifications. + specifying types and function specifications: 

 -type my_type() :: atom() | integer().
@@ -200,32 +213,36 @@ behaviour_info(callbacks) -> Callbacks.

The description is based on EEP8 - - Types and function specifications - which will not be further updated. + Types and function specifications, + which is not to be further updated.

Comments -

Comments may be placed anywhere in a module except within strings - and quoted atoms. The comment begins with the character "%", +

Comments can be placed anywhere in a module except within strings + and quoted atoms. A comment begins with the character "%", continues up to, but does not include the next end-of-line, and - has no effect. Note that the terminating end-of-line has + has no effect. Notice that the terminating end-of-line has the effect of white space.

- The module_info/0 and module_info/1 functions + module_info/0 and module_info/1 functions

The compiler automatically inserts the two special, exported - functions into each module: Module:module_info/0 and - Module:module_info/1. These functions can be called to - retrieve information about the module.

+ functions into each module:

+ + Module:module_info/0 + Module:module_info/1 + +

These functions can be called to retrieve information + about the module.

module_info/0 -

The module_info/0 function in each module returns +

The module_info/0 function in each module, returns a list of {Key,Value} tuples with information about the module. Currently, the list contain tuples with the following Keys: module, attributes, compile, @@ -235,7 +252,7 @@ behaviour_info(callbacks) -> Callbacks.

module_info/1 -

The call module_info(Key), where key is an atom, +

The call module_info(Key), where Key is an atom, returns a single piece of information about the module.

The following values are allowed for Key:

@@ -243,44 +260,46 @@ behaviour_info(callbacks) -> Callbacks. module -

Return an atom representing the module name.

+

Returns an atom representing the module name.

 attributes -

Return a list of {AttributeName,ValueList} tuples, +

Returns a list of {AttributeName,ValueList} tuples, where AttributeName is the name of an attribute, - and ValueList is a list of values. Note: a given - attribute may occur more than once in the list with different + and ValueList is a list of values. Notice that a given + attribute can occur more than once in the list with different values if the attribute occurs more than once in the module.

-

The list of attributes will be empty if - the module has been stripped with - beam_lib(3).

+

The list of attributes becomes empty if + the module is stripped with the + beam_lib(3) + module (in STDLIB).

 compile -

Return a list of tuples containing information about - how the module was compiled. This list will be empty if - the module has been stripped with - beam_lib(3).

+

Returns a list of tuples with information about + how the module was compiled. This list is empty if + the module has been stripped with the + beam_lib(3) + module (in STDLIB).

 md5 -

Return a binary representing the MD5 checksum of the module.

+

Returns a binary representing the MD5 checksum of the module.

 exports -

Return a list of {Name,Arity} tuples with +

Returns a list of {Name,Arity} tuples with all exported functions in the module.

 functions -

Return a list of {Name,Arity} tuples with +

Returns a list of {Name,Arity} tuples with all functions in the module.

 diff --git a/system/doc/reference_manual/patterns.xml b/system/doc/reference_manual/patterns.xml index 1611002fa1..2163583636 100644 --- a/system/doc/reference_manual/patterns.xml +++ b/system/doc/reference_manual/patterns.xml @@ -40,7 +40,7 @@ term. If the matching succeeds, any unbound variables in the pattern become bound. If the matching fails, a run-time error occurs.

-

Examples:

+

Examples:

 1> X.
 ** 1: variable 'X' is unbound **
diff --git a/system/doc/reference_manual/ports.xml b/system/doc/reference_manual/ports.xml
index 621af10624..e5dc99641b 100644
--- a/system/doc/reference_manual/ports.xml
+++ b/system/doc/reference_manual/ports.xml
@@ -4,7 +4,7 @@
 
   

     
-      20042013
+      20042015
       Ericsson AB. All Rights Reserved.
     
     
@@ -28,9 +28,12 @@
     
     ports.xml
   

-  
Examples of how to use ports and port drivers can be found in
-    Interoperability Tutorial. The BIFs mentioned are as usual
-    documented in erlang(3).

+  
Examples of how to use ports and port drivers are provided in
+    
+    Interoperability Tutorial.
+    For information about the BIFs mentioned, see the
+    erlang(3) manual
+    page in ERTS.

 
   

     Ports
@@ -39,29 +42,34 @@
       provide a byte-oriented interface to an external program. When a
       port has been created, Erlang can communicate with it by sending
       and receiving lists of bytes, including binaries.

-    
The Erlang process which creates a port is said to be
+    
The Erlang process creating a port is said to be
       the port owner, or the connected process of
-      the port. All communication to and from the port should go via
-      the port owner. If the port owner terminates, so will the port
+      the port. All communication to and from the port must go through
+      the port owner. If the port owner terminates, so does the port
       (and the external program, if it is written correctly).

     
The external program resides in another OS process. By default,
-      it should read from standard input (file descriptor 0) and write
+      it reads from standard input (file descriptor 0) and writes
       to standard output (file descriptor 1). The external program
-      should terminate when the port is closed.

+      is to terminate when the port is closed.

   

 
   

     Port Drivers
-    
It is also possible to write a driver in C according to certain
+    
It is possible to write a driver in C according to certain
       principles and dynamically link it to the Erlang runtime system.
       The linked-in driver looks like a port from the Erlang
       programmer's point of view and is called a port driver.

     
-      
An erroneous port driver will cause the entire Erlang runtime
+      
An erroneous port driver causes the entire Erlang runtime
         system to leak memory, hang or crash.

     
-    
Port drivers are documented in erl_driver(4),
-      driver_entry(1) and erl_ddll(3).

+    
For information about port drivers, see the
+      erl_driver(4)
+      manual page in ERTS,
+      driver_entry(1)
+      manual page in ERTS, and
+      erl_ddll(3)
+      manual page in Kernel.

   

 
   

@@ -70,53 +78,74 @@
     
         open_port(PortName, PortSettings
-        Returns a port identifier Portas the result of opening a new Erlang port. Messages can be sent to and received from a port identifier, just like a pid. Port identifiers can also be linked to or registered under a name using link/1and register/2.
+        Returns a port identifier
+        Port as the result of opening a new Erlang port.
+        Messages can be sent to, and received from, a port identifier,
+        just like a pid. Port identifiers can also be linked to
+        using link/1, or registered under a name using
+        register/2.
       
-      Port Creation BIF.
+      Port Creation BIF

       
     

     
PortName is usually a tuple {spawn,Command}, where
       the string Command is the name of the external program.
-      The external program runs outside the Erlang workspace unless a
-      port driver with the name Command is found. If found, that
-      driver is started.

+      The external program runs outside the Erlang workspace, unless a
+      port driver with the name Command is found. If Command
+      is found, that driver is started.

     
PortSettings is a list of settings (options) for the port.
-      The list typically contains at least a tuple {packet,N}
+      The list typically contains at least a tuple {packet,N},
       which specifies that data sent between the port and the external
       program are preceded by an N-byte length indicator. Valid values
-      for N are 1, 2 or 4. If binaries should be used instead of lists
+      for N are 1, 2, or 4. If binaries are to be used instead of lists
       of bytes, the option binary must be included.

     
The port owner Pid can communicate with the port
       Port by sending and receiving messages. (In fact, any
       process can send the messages to the port, but the port owner must
       be identified in the message).

-    
As of OTP-R16 messages sent to ports are delivered truly
+    
As of Erlang/OTP R16, messages sent to ports are delivered truly
       asynchronously. The underlying implementation previously
       delivered messages to ports synchronously. Message passing has
-      however always been documented as an asynchronous operation, so
-      this should not be an issue for an Erlang program communicating
-      with ports, unless false assumptions about ports has been made.

-    
Below, Data must be an I/O list. An I/O list is a binary
-      or a (possibly deep) list of binaries or integers in the range
-      0..255.

+      however always been documented as an asynchronous operation. Hence,
+      this is not to be an issue for an Erlang program communicating
+      with ports, unless false assumptions about ports have been made.

+    
In the following tables of examples, Data must be an I/O list.
+      An I/O list is a binary or a (possibly deep) list of binaries
+      or integers in the range 0..255:

     
+      
+        Message
+        Description
+      
         {Pid,{command,Data}}
-        Sends Datato the port.
+        Sends Data to the port.
       
         {Pid,close}
-        Closes the port. Unless the port is already closed, the port replies with {Port,closed}when all buffers have been flushed and the port really closes.
+        Closes the port. Unless the
+        port is already closed, the port replies with
+        {Port,closed} when all buffers have been flushed
+        and the port really closes.
       
         {Pid,{connect,NewPid}}
-        Sets the port owner of Portto NewPid. Unless the port is already closed, the port replies with{Port,connected}to the old port owner. Note that the old port owner is still linked to the port, but the new port owner is not.
+        Sets the port owner of
+        Portto NewPid. Unless the port is already closed,
+        the port replies with{Port,connected} to the old
+        port owner. Note that the old port owner is still linked
+        to the port, but the new port owner is not.
       
-      Messages Sent To a Port.
+      Messages Sent To a Port

       
       
       
     

+    

     
+      
+        Message
+        Description
+      
         {Port,{data,Data}}
-        Datais received from the external program.
+        Data is received from the external program.
       
         {Port,closed}
@@ -124,20 +153,24 @@
       
         {Port,connected}
-        Reply to Port ! {Pid,{connect,NewPid}}
+        Reply to Port ! {Pid,{connect,NewPid}}.
       
         {'EXIT',Port,Reason}
         If the port has terminated for some reason.
       
-      Messages Received From a Port.
+      Messages Received From a Port

       
       
       
       
     

     
Instead of sending and receiving messages, there are also a
-      number of BIFs that can be used.

+      number of BIFs that can be used:

     
+      
+        Port BIF
+        Description
+      
         port_command(Port,Data)
-        Sends Datato the port.
+        Sends Data to the port.
       
         port_close(Port)
@@ -145,7 +178,10 @@
       
         port_connect(Port,NewPid)
-        Sets the port owner of Portto NewPid. The old port owner Pidstays linked to the port and have to call unlink(Port)if this is not desired.
+        Sets the port owner of
+        Portto NewPid. The old port owner Pid
+        stays linked to the port and must call unlink(Port)
+        if this is not desired.
       
         erlang:port_info(Port,Item)
@@ -155,9 +191,9 @@
         erlang:ports()
         Returns a list of all ports on the current node.
       
-      Port BIFs.
+      Port BIFs

       
       
       
       
     

-    
There are some additional BIFs that only apply to port drivers:
+    
Some additional BIFs that apply to port drivers:
       port_control/3 and erlang:port_call/3.

   

 
diff --git a/system/doc/reference_manual/processes.xml b/system/doc/reference_manual/processes.xml
index 95ae0672ec..32af6d4480 100644
--- a/system/doc/reference_manual/processes.xml
+++ b/system/doc/reference_manual/processes.xml
@@ -4,7 +4,7 @@
 
   

     
-      20032013
+      20032015
       Ericsson AB. All Rights Reserved.
     
     
@@ -32,8 +32,8 @@
   

     Processes
     
Erlang is designed for massive concurrency. Erlang processes are
-      light-weight (grow and shrink dynamically) with small memory
-      footprint, fast to create and terminate and the scheduling
+      lightweight (grow and shrink dynamically) with small memory
+      footprint, fast to create and terminate, and the scheduling
       overhead is low.

   

 
@@ -46,10 +46,10 @@ spawn(Module, Name, Args) -> pid()
   Args = [Arg1,...,ArgN]
     ArgI = term()

spawn creates a new process and returns the pid.

-

The new process will start executing in - Module:Name(Arg1,...,ArgN) where the arguments is +

The new process starts executing in + Module:Name(Arg1,...,ArgN) where the arguments are the elements of the (possible empty) Args argument list.

-

There exist a number of other spawn BIFs, for example +

There exist a number of other spawn BIFs, for example, spawn/4 for spawning a process at another node.

@@ -59,19 +59,26 @@ spawn(Module, Name, Args) -> pid() BIFs for registering a process under a name. The name must be an atom and is automatically unregistered if the process terminates:

+ + BIF + Description + register(Name, Pid) Associates the name Name, an atom, with the process Pid. registered() - Returns a list of names which have been registered usingregister/2. + Returns a list of names that + have been registered using register/2. whereis(Name) - Returns the pid registered under Name, orundefinedif the name is not registered. + Returns the pid registered + under Name, or undefined if the name is not + registered. - Name Registration BIFs. + Name Registration BIFs
@@ -79,22 +86,27 @@ spawn(Module, Name, Args) -> pid() Process Termination

When a process terminates, it always terminates with an - exit reason. The reason may be any term.

+ exit reason. The reason can be any term.

A process is said to terminate normally, if the exit reason is the atom normal. A process with no more code to execute terminates normally.

-

A process terminates with exit reason {Reason,Stack} +

A process terminates with an exit reason {Reason,Stack} when a run-time error occurs. See - Error and Error Handling.

-

A process can terminate itself by calling one of the BIFs - exit(Reason), - erlang:error(Reason), erlang:error(Reason, Args), - erlang:fault(Reason) or erlang:fault(Reason, Args). - The process then terminates with reason Reason for + Exit Reasons.

+

A process can terminate itself by calling one of the + following BIFs:

+ + exit(Reason) + erlang:error(Reason) + erlang:error(Reason, Args) + erlang:fault(Reason) + erlang:fault(Reason, Args) + +

The process then terminates with reason Reason for exit/1 or {Reason,Stack} for the others.

-

A process may also be terminated if it receives an exit signal +

A process can also be terminated if it receives an exit signal with another exit reason than normal, see - Error Handling below.

+ Error Handling.

@@ -113,35 +125,38 @@ spawn(Module, Name, Args) -> pid() Links

Two processes can be linked to each other. A link between two processes Pid1 and Pid2 is created - by Pid1 calling the BIF link(Pid2) (or vice versa). + by Pid1 calling the BIF link(Pid2) (or conversely). There also exist a number of spawn_link BIFs, which spawn and link to a process in one operation.

Links are bidirectional and there can only be one link between two processes. Repeated calls to link(Pid) have no effect.

A link can be removed by calling the BIF unlink(Pid).

Links are used to monitor the behaviour of other processes, see - Error Handling below.

+ Error Handling.

Error Handling

Erlang has a built-in feature for error handling between - processes. Terminating processes will emit exit signals to all - linked processes, which may terminate as well or handle the exit + processes. Terminating processes emit exit signals to all + linked processes, which can terminate as well or handle the exit in some way. This feature can be used to build hierarchical program structures where some processes are supervising other - processes, for example restarting them if they terminate + processes, for example, restarting them if they terminate abnormally.

-

Refer to OTP Design Principles for more information about - OTP supervision trees, which uses this feature.

+

See + OTP Design Principles for more information about + OTP supervision trees, which use this feature.

Emitting Exit Signals -

When a process terminates, it will terminate with an exit reason as explained in Process Termination above. This exit reason is emitted in +

When a process terminates, it terminates with an + exit reason as explained in + Process Termination. This exit reason is emitted in an exit signal to all linked processes.

A process can also call the function exit(Pid,Reason). - This will result in an exit signal with exit reason + This results in an exit signal with exit reason Reason being emitted to Pid, but does not affect the calling process.

@@ -156,14 +171,14 @@ spawn(Module, Name, Args) -> pid()

A process can be set to trap exit signals by calling:

 process_flag(trap_exit, true)
-

When a process is trapping exits, it will not terminate when +

When a process is trapping exits, it does not terminate when an exit signal is received. Instead, the signal is transformed - into a message {'EXIT',FromPid,Reason} which is put into - the mailbox of the process just like a regular message.

+ into a message {'EXIT',FromPid,Reason}, which is put into + the mailbox of the process, just like a regular message.

An exception to the above is if the exit reason is kill, - that is if exit(Pid,kill) has been called. This will - unconditionally terminate the process, regardless of if it is - trapping exit signals or not.

+ that is if exit(Pid,kill) has been called. This + unconditionally terminates the process, regardless of if it is + trapping exit signals.

@@ -180,12 +195,12 @@ process_flag(trap_exit, true)

If Pid2 does not exist, the 'DOWN' message is sent immediately with Reason set to noproc.

Monitors are unidirectional. Repeated calls to - erlang:monitor(process, Pid) will create several, - independent monitors and each one will send a 'DOWN' message when + erlang:monitor(process, Pid) creates several + independent monitors, and each one sends a 'DOWN' message when Pid terminates.

A monitor can be removed by calling erlang:demonitor(Ref).

-

It is possible to create monitors for processes with registered +

Monitors can be created for processes with registered names, also at other nodes.

diff --git a/system/doc/reference_manual/records.xml b/system/doc/reference_manual/records.xml index 04766531df..3294255af9 100644 --- a/system/doc/reference_manual/records.xml +++ b/system/doc/reference_manual/records.xml @@ -32,16 +32,19 @@ elements. It has named fields and is similar to a struct in C. Record expressions are translated to tuple expressions during compilation. Therefore, record expressions are not understood by - the shell unless special actions are taken. See shell(3) - for details.

-

More record examples can be found in Programming Examples.

+ the shell unless special actions are taken. For details, see the + shell(3) + manual page in STDLIB.

+

More examples are provided in + + Programming Examples.

Defining Records

A record definition consists of the name of the record, followed by the field names of the record. Record and field names must be atoms. Each field can be given an optional default value. - If no default value is supplied, undefined will be used.

+ If no default value is supplied, undefined is used.

 -record(Name, {Field1 [= Value1],
                ...
@@ -60,17 +63,18 @@
       the corresponding expression ExprI:

     
 #Name{Field1=Expr1,...,FieldK=ExprK}

-    
The fields may be in any order, not necessarily the same order as
+    
The fields can be in any order, not necessarily the same order as
       in the record definition, and fields can be omitted. Omitted
-      fields will get their respective default value instead.

-    
If several fields should be assigned the same value,
+      fields get their respective default value instead.

+    
If several fields are to be assigned the same value,
       the following construction can be used:

     
 #Name{Field1=Expr1,...,FieldK=ExprK, _=ExprL}

-    
Omitted fields will then get the value of evaluating ExprL
+    
Omitted fields then get the value of evaluating ExprL
       instead of their default values. This feature was added in
       Erlang 5.1/OTP R8 and is primarily intended to be used to create
-      patterns for ETS and Mnesia match functions. Example:

+      patterns for ETS and Mnesia match functions.

+    
Example:

     
 -record(person, {name, phone, address}).
 
@@ -84,13 +88,13 @@ lookup(Name, Tab) ->
     Accessing Record Fields
     
 Expr#Name.Field

-    
Returns the value of the specified field. Expr should
+    
Returns the value of the specified field. Expr is to
       evaluate to a Name record.

     
The following expression returns the position of the specified
       field in the tuple representation of the record:

     
 #Name.Field

-    
Example:

+    
Example:

     
 -record(person, {name, phone, address}).
 
@@ -104,8 +108,8 @@ lookup(Name, List) ->
     Updating Records
     
 Expr#Name{Field1=Expr1,...,FieldK=ExprK}

-    
Expr should evaluate to a Name record. Returns a
-      copy of this record, with the value of each specified field
+    
Expr is to evaluate to a Name record. A
+      copy of this record is returned, with the value of each specified field
       FieldI changed to the value of evaluating the corresponding
       expression ExprI. All other fields retain their old
       values.

@@ -116,17 +120,17 @@ Expr#Name{Field1=Expr1,...,FieldK=ExprK}

     Records in Guards
     
Since record expressions are expanded to tuple expressions,
       creating records and accessing record fields are allowed in
-      guards. However all subexpressions, for example for field
-      initiations, must of course be valid guard expressions as well.
-      Examples:

+      guards. However all subexpressions, for example, for field
+      initiations, must be valid guard expressions as well.

+    
Examples:

     
 handle(Msg, State) when Msg==#msg{to=void, no=3} ->
     ...
 
 handle(Msg, State) when State#state.running==true ->
     ...
-    
There is also a type test BIF is_record(Term, RecordTag).
-      Example:

+    
There is also a type test BIF is_record(Term, RecordTag).

+    
Example:

     
 is_person(P) when is_record(P, person) ->
     true;
@@ -136,18 +140,18 @@ is_person(_P) ->
 
   

     Records in Patterns
-    
A pattern that will match a certain record is created the same
+    
A pattern that matches a certain record is created in the same
       way as a record is created:

     
 #Name{Field1=Expr1,...,FieldK=ExprK}

-    
In this case, one or more of Expr1...ExprK may be
+    
In this case, one or more of Expr1...ExprK can be
       unbound variables.

   

 
   

-    Nested records
-    
Beginning with R14 parentheses when accessing or updating nested
-      records can be omitted. Assuming we have the following record
+    Nested Records
+    
Beginning with Erlang/OTP R14, parentheses when accessing or updating nested
+      records can be omitted. Assume the following record
       definitions:

     
 -record(nrec0, {name = "nested0"}).
@@ -156,12 +160,12 @@ is_person(_P) ->
 
 N2 = #nrec2{},
     

-    
Before R14 you would have needed to use parentheses as following:

+    
Before R14, parentheses were needed as follows:

     
 "nested0" = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0.name,
 N0n = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0{name = "nested0a"},
     

-    
Since R14 you can also write:

+    
Since R14, the following can also be written:

     
 "nested0" = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
 N0n = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = "nested0a"},

@@ -170,23 +174,23 @@ N0n = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = "nested0a"},

   

     Internal Representation of Records
     
Record expressions are translated to tuple expressions during
-      compilation. A record defined as

+      compilation. A record defined as:

     
 -record(Name, {Field1,...,FieldN}).

-    
is internally represented by the tuple

+    
is internally represented by the tuple:

     
 {Name,Value1,...,ValueN}

-    
where each ValueI is the default value for FieldI.

+    
Here each ValueI is the default value for FieldI.

     
To each module using records, a pseudo function is added
       during compilation to obtain information about records:

     
 record_info(fields, Record) -> [Field]
 record_info(size, Record) -> Size

-    
Size is the size of the tuple representation, that is
+    
Size is the size of the tuple representation, that is,
       one more than the number of fields.

     
In addition, #Record.Name returns the index in the tuple
-    representation of Name of the record Record.
-    Name must be an atom.

+      representation of Name of the record Record.

+    
Name must be an atom.

   

 
 
diff --git a/system/doc/reference_manual/typespec.xml b/system/doc/reference_manual/typespec.xml
index d1584d2b98..0891dbaa9b 100644
--- a/system/doc/reference_manual/typespec.xml
+++ b/system/doc/reference_manual/typespec.xml
@@ -34,43 +34,46 @@
     

       Erlang is a dynamically typed language. Still, it comes with a
       notation for declaring sets of Erlang terms to form a particular
-      type, effectively forming a specific sub-type of the set of all
+      type. This effectively forms specific subtypes of the set of all
       Erlang terms.
     

     

       Subsequently, these types can be used to specify types of record fields
-      and the argument and return types of functions.
-    

-    

-      Type information can be used to document function interfaces,
-      provide more information for bug detection tools such as Dialyzer,
-      and can be exploited by documentation tools such as Edoc for
-      generating program documentation of various forms.
-      It is expected that the type language described in this document will
-      supersede and replace the purely comment-based @type and
-      @spec declarations used by Edoc.
-    

+      and also the argument and return types of functions.
+    

+    

+      Type information can be used for the following:

+    
+      To document function interfaces
+      To provide more information for bug detection tools,
+      such as Dialyzer
+      To be exploited by documentation tools, such as EDoc, for
+      generating program documentation of various forms
+    
+    
It is expected that the type language described in this section
+      supersedes and replaces the purely comment-based @type and
+      @spec declarations used by EDoc.
Types and their Syntax

Types describe sets of Erlang terms. - Types consist and are built from a set of predefined types - (e.g. integer(), atom(), pid(), ...) - described below. - Predefined types represent a typically infinite set of Erlang terms which + Types consist of, and are built from, a set of predefined types, + for example, integer(), atom(), and pid(). + Predefined types represent a typically infinite set of Erlang terms that belong to this type. For example, the type atom() stands for the set of all Erlang atoms.

- For integers and atoms, we allow for singleton types (e.g. the integers - -1 and 42 or the atoms 'foo' and 'bar'). + For integers and atoms, it is allowed for singleton types; for example, + the integers + -1 and 42, or the atoms 'foo' and 'bar'). All other types are built using unions of either predefined types or singleton types. In a type union between a type and one - of its sub-types the sub-type is absorbed by the super-type and - the union is subsequently treated as if the sub-type was not a + of its subtypes, the subtype is absorbed by the supertype. Thus, + the union is then treated as if the subtype was not a constituent of the union. For example, the type union: 

  atom() | 'bar' | integer() | 42
@@ -79,13 +82,13 @@ 

  atom() | integer()

- Because of sub-type relations that exist between types, types - form a lattice where the topmost element, any(), denotes + Because of subtype relations that exist between types, types + form a lattice where the top-most element, any(), denotes the set of all Erlang terms and the bottom-most element, none(), denotes the empty set of terms.

- The set of predefined types and the syntax for types is given below: + The set of predefined types and the syntax for types follows: 


     The general form of bitstrings is <<_:M, _:_*N>>,
     where M and N are positive integers. It denotes a
-    bitstring that is M + (k*N) bits long (i.e., a bitstring that
+    bitstring that is M + (k*N) bits long (that is, a bitstring that
     starts with M bits and continues with k segments of
     N bits each, where k is also a positive integer).
     The notations <<_:_*N>>, <<_:M>>,
     and <<>> are convenient shorthands for the cases
-    that M, N, or both, respectively, are zero.
+    that M or N, or both, are zero.
   

   

     Because lists are commonly used, they have shorthand type notations. 
     The types list(T) and nonempty_list(T) have the shorthands
     [T] and [T,...], respectively.
-    The only difference between the two shorthands is that [T] may be an 
-    empty list but [T,...] may not.
+    The only difference between the two shorthands is that [T] can be an
+    empty list but [T,...] cannot.
   

   

-    Notice that the shorthand for list(), i.e. the list of
+    Notice that the shorthand for list(), that is, the list of
     elements of unknown type, is [_] (or [any()]), not []. 
     The notation [] specifies the singleton type for the empty list.
   

@@ -172,7 +175,7 @@
   

   
-      Built-in typeDefined as
+      Built-in typeDefined as
     
       term()any()
@@ -237,6 +240,7 @@
     
       no_return()none() 
     
+    Built-in types, predefined aliases
   

     
     

   

   In addition, the following three built-in types exist and can be
@@ -245,7 +249,8 @@
   

   
-      Built-in typeCould be thought defined by the syntax
+      Built-in type
+        Can be thought defined by the syntax
     
       non_neg_integer()0..
@@ -256,6 +261,7 @@
     
       neg_integer()..-1
     
+    Additional built-in types
   

     
     

   
   

@@ -278,109 +284,118 @@
     define the set of Erlang terms one would expect.
   

   

-    Also for convenience, we allow for record notation to be used. 
-    Records are just shorthands for the corresponding tuples.
+    Also for convenience, record notation is allowed to be used.
+    Records are shorthands for the corresponding tuples:
   

   
   Record :: #Erlang_Atom{}
           | #Erlang_Atom{Fields}

   

-    Records have been extended to possibly contain type information. 
-    This is described in the sub-section "Type information in record declarations" below.
+    Records are extended to possibly contain type information.
+    This is described in 
+    Type Information in Record Declarations.
   

   
-	  
Map types, both map() and #{ ... }, are considered experimental during OTP 17.

-	  
No type information of maps pairs, only the containing map types, are used by Dialyzer in OTP 17.

+    
Map types, both map() and #{...},
+      are considered experimental during OTP 17.

+    
No type information of maps pairs, only the containing map types,
+      are used by Dialyzer in OTP 17.
- +
- Type declarations of user-defined types + Type Declarations of User-Defined Types

As seen, the basic syntax of a type is an atom followed by closed - parentheses. New types are declared using '-type' and '-opaque' + parentheses. New types are declared using -type and -opaque compiler attributes as in the following: 

   -type my_struct_type() :: Type.
   -opaque my_opaq_type() :: Type.

- where the type name is an atom ('my_struct_type' in the above) - followed by parentheses. Type is a type as defined in the + The type name is the atom my_struct_type, + followed by parentheses. Type is a type as defined in the previous section. - A current restriction is that Type can contain only predefined types, - or user-defined types which are either module-local (i.e., with a - definition that is present in the code of the module) or are remote - types (i.e., types defined in and exported by other modules; see below). - For module-local types, the restriction that their definition + A current restriction is that Type can contain + only predefined types, + or user-defined types which are either of the following: +

+ + Module-local type, that is, with a + definition that is present in the code of the module + Remote type, that is, type defined in, and exported by, + other modules; more about this soon. + +

For module-local types, the restriction that their definition exists in the module is enforced by the compiler and results in a - compilation error. (A similar restriction currently exists for records.) -

+ compilation error. (A similar restriction currently exists for records.)

Type declarations can also be parameterized by including type variables between the parentheses. The syntax of type variables is the same as - Erlang variables (starts with an upper case letter). - Naturally, these variables can - and should - appear on the RHS of the - definition. A concrete example appears below: + Erlang variables, that is, starts with an upper-case letter. + Naturally, these variables can - and is to - appear on the RHS of the + definition. A concrete example follows: 

   -type orddict(Key, Val) :: [{Key, Val}].

- A module can export some types in order to declare that other modules + A module can export some types to declare that other modules are allowed to refer to them as remote types. - This declaration has the following form: + This declaration has the following form:

   -export_type([T1/A1, ..., Tk/Ak]).
- where the Ti's are atoms (the name of the type) and the Ai's are their - arguments. An example is given below: +

Here the Ti's are atoms (the name of the type) and the Ai's are their + arguments

+

Example:

   -export_type([my_struct_type/0, orddict/2]).
- Assuming that these types are exported from module 'mod' then - one can refer to them from other modules using remote type expressions - like those below: +

Assuming that these types are exported from module 'mod', + you can refer to them from other modules using remote type expressions + like the following:

   mod:my_struct_type()
   mod:orddict(atom(), term())
- One is not allowed to refer to types which are not declared as exported. +

It is not allowed to refer to types that are not declared as exported.

Types declared as opaque represent sets of terms whose - structure is not supposed to be visible in any way outside of - their defining module (i.e., only the module defining them is - allowed to depend on their term structure). Consequently, such + structure is not supposed to be visible from outside of + their defining module. That is, only the module defining them + is allowed to depend on their term structure. Consequently, such types do not make much sense as module local - module local - types are not accessible by other modules anyway - and should - always be exported. + types are not accessible by other modules anyway - and is + always to be exported.

- - +
- Type information in record declarations + + Type Information in Record Declarations

- The types of record fields can be specified in the declaration of the - record. The syntax for this is: + The types of record fields can be specified in the declaration of the + record. The syntax for this is as follows: 

   -record(rec, {field1 :: Type1, field2, field3 :: Type3}).

For fields without type annotations, their type defaults to any(). - I.e., the above is a shorthand for: + That is, the previous example is a shorthand for the following: 

   -record(rec, {field1 :: Type1, field2 :: any(), field3 :: Type3}).

In the presence of initial values for fields, - the type must be declared after the initialization as in the following: + the type must be declared after the initialization, as follows: 

   -record(rec, {field1 = [] :: Type1, field2, field3 = 42 :: Type3}).

- Naturally, the initial values for fields should be compatible - with (i.e. a member of) the corresponding types. - This is checked by the compiler and results in a compilation error - if a violation is detected. For fields without initial values, - the singleton type 'undefined' is added to all declared types. + The initial values for fields are to be compatible + with (that is, a member of) the corresponding types. + This is checked by the compiler and results in a compilation error + if a violation is detected. For fields without initial values, + the singleton type 'undefined' is added to all declared types. In other words, the following two record declarations have identical effects:

@@ -398,13 +413,13 @@

Any record, containing type information or not, once defined, - can be used as a type using the syntax: + can be used as a type using the following syntax: 

  #rec{}

In addition, the record fields can be further specified when using - a record type by adding type information about the field in - the following manner: + a record type by adding type information about the field + as follows: 

  #rec{some_field :: Type}

@@ -414,16 +429,16 @@

- Specifications for functions + Specifications for Functions

A specification (or contract) for a function is given using the new - compiler attribute '-spec'. The general format is as follows: + compiler attribute -spec. The general format is as follows: 

   -spec Module:Function(ArgType1, ..., ArgTypeN) -> ReturnType.

- The arity of the function has to match the number of arguments, - or else a compilation error occurs. + The arity of the function must match the number of arguments, + else a compilation error occurs.

This form can also be used in header files (.hrl) to declare type @@ -432,7 +447,7 @@ explicitly) import these functions.

- For most uses within a given module, the following shorthand suffices: + Within a given module, the following shorthand suffice in most cases: 

   -spec Function(ArgType1, ..., ArgTypeN) -> ReturnType.
@@ -450,8 +465,8 @@ ; (T4, T5) -> T6.

A current restriction, which currently results in a warning - (OBS: not an error) by the compiler, is that the domains of - the argument types cannot be overlapping. + (not an error) by the compiler, is that the domains of + the argument types cannot overlap. For example, the following specification results in a warning: 

@@ -466,41 +481,43 @@
     
   -spec id(X) -> X.

     

-      However, note that the above specification does not restrict the input 
-      and output type in any way. 
-      We can constrain these types by guard-like subtype constraints
+      Notice that the above specification does not restrict the input
+      and output type in any way.
+      These types can be constrained by guard-like subtype constraints
       and provide bounded quantification:
     

     
  -spec id(X) -> X when X :: tuple().

     

       Currently, the :: constraint (read as is_subtype) is
-      the only guard constraint which can be used in the 'when'
+      the only guard constraint that can be used in the 'when'
       part of a '-spec' attribute.
     

     
       

-      The above function specification, using multiple occurrences of
-      the same type variable, provides more type information than the
-      function specification below where the type variables are missing:
+      The above function specification uses multiple occurrences of
+      the same type variable. That provides more type information than the
+      following function specification, where the type variables are missing:
       

       
  -spec id(tuple()) -> tuple().

       

 	The latter specification says that the function takes some tuple
-	and returns some tuple, while the one with the X type
+	and returns some tuple. The specification with the X type
 	variable specifies that the function takes a tuple and returns
 	the same tuple.
       

       

-	However, it's up to the tools that process the specs to choose
-	whether to take this extra information into account or ignore it.
+	However, it is up to the tools that process the specificationss
+        to choose whether to take this extra information into account
+        or not.
       

     
     

-      The scope of an :: constraint is the 
-      (...) -> RetType 
-      specification after which it appears. To avoid confusion, 
-      we suggest that different variables are used in different
-      constituents of an overloaded contract as in the example below:
+      The scope of a :: constraint is the
+      (...) -> RetType
+      specification after which it appears. To avoid confusion,
+      it is suggested that different variables are used in different
+      constituents of an overloaded contract, as shown in the
+      following example:
     

     
   -spec foo({X, integer()}) -> X when X :: atom()
@@ -511,19 +528,20 @@
       

       
  -spec id(X) -> X when is_subtype(X, tuple()).

       

-	but its use is discouraged. It will be taken out in a future
+	but its use is discouraged. It will be removed in a future
 	Erlang/OTP release.
       

     
     

       Some functions in Erlang are not meant to return; 
       either because they define servers or because they are used to 
-      throw exceptions as the function below:
+      throw exceptions, as in the following function:
     

     
  my_error(Err) -> erlang:throw({error, Err}).

     

-      For such functions we recommend the use of the special no_return()
-      type for their "return", via a contract of the form:
+      For such functions, it is recommended to use the special
+      no_return() type for their "return", through a contract
+      of the following form:
     

     
  -spec my_error(term()) -> no_return().
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