Update Erlang Reference Manual

Language cleaned up by the technical writers xsipewe and tmanevik
from Combitech. Proofreading and corrections by Hans Bolinder.

1 files changed, 41 insertions, 38 deletions

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 @@
 <chapter>
   <header>
     <copyright>
-      <year>2003</year><year>2013</year>
+      <year>2003</year><year>2015</year>
       <holder>Ericsson AB. All Rights Reserved.</holder>
     </copyright>
     <legalnotice>
@@ -38,7 +38,7 @@
       clause body, separated by <c>-></c>.</p>
     <p>A clause <em>head</em> consists of the function name, an
       argument list, and an optional guard sequence
-      beginning with the keyword <c>when</c>.</p>
+      beginning with the keyword <c>when</c>:</p>
     <pre>
 Name(Pattern11,...,Pattern1N) [when GuardSeq1] ->
     Body1;
@@ -48,9 +48,9 @@ Name(PatternK1,...,PatternKN) [when GuardSeqK] ->
     <p>The function name is an atom. Each argument is a pattern.</p>
     <p>The number of arguments <c>N</c> is the <em>arity</em> 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.</p>
+      different functions.</p>
     <p>A function named <c>f</c> in the module <c>m</c> and with arity
       <c>N</c> is often denoted as <c>m:f/N</c>.</p>
     <p>A clause <em>body</em> consists of a sequence of expressions
@@ -60,8 +60,8 @@ Expr1,
 ...,
 ExprN</pre>
     <p>Valid Erlang expressions and guard sequences are described in
-      <seealso marker="expressions">Erlang Expressions</seealso>.</p>
-    <p>Example:</p>
+      <seealso marker="expressions">Expressions</seealso>.</p>
+    <p><em>Example:</em></p>
     <pre>
 fact(N) when N>0 ->  % first clause head
     N * fact(N-1);   % first clause body
@@ -75,23 +75,23 @@ fact(0) ->           % second clause head
     <title>Function Evaluation</title>
     <p>When a function <c>m:f/N</c> is called, first the code for
       the function is located. If the function cannot be found, an
-      <c>undef</c> run-time error will occur. Note that the function
+      <c>undef</c> runtime error occurs. Notice that the function
       must be exported to be visible outside the module it is defined
       in.</p>
     <p>If the function is found, the function clauses are scanned
-      sequentially until a clause is found that fulfills the following
-      two conditions:</p>
+      sequentially until a clause is found that fulfills both of
+      the following two conditions:</p>
     <list type="ordered">
-      <item>the patterns in the clause head can be successfully
-       matched against the given arguments, and</item>
-      <item>the guard sequence, if any, is true.</item>
+      <item>The patterns in the clause head can be successfully
+       matched against the given arguments.</item>
+      <item>The guard sequence, if any, is true.</item>
     </list>
     <p>If such a clause cannot be found, a <c>function_clause</c>
-      run-time error will occur.</p>
+      runtime error occurs.</p>
     <p>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.</p>
-    <p>Example: Consider the function <c>fact</c>:</p>
+    <p>Consider the function <c>fact</c>:</p>
     <pre>
 -module(m).
 -export([fact/1]).
@@ -100,17 +100,17 @@ fact(N) when N>0 ->
     N * fact(N-1);
 fact(0) ->
     1.</pre>
-    <p>Assume we want to calculate factorial for 1:</p>
+    <p>Assume that you want to calculate the factorial for 1:</p>
     <pre>
 1> <input>m:fact(1).</input></pre>
     <p>Evaluation starts at the first clause. The pattern <c>N</c> is
-      matched against the argument 1. The matching succeeds and
-      the guard (<c>N>0</c>) is true, thus <c>N</c> is bound to 1 and
+      matched against argument 1. The matching succeeds and
+      the guard (<c>N>0</c>) is true, thus <c>N</c> is bound to 1, and
       the corresponding body is evaluated:</p>
     <pre>
 <input>N * fact(N-1)</input> => (N is bound to 1)
 <input>1 * fact(0)</input></pre>
-    <p>Now <c>fact(0)</c> is called and the function clauses are
+    <p>Now, <c>fact(0)</c> is called, and the function clauses are
       scanned sequentially again. First, the pattern <c>N</c> is
       matched against 0. The matching succeeds, but the guard
       (<c>N>0</c>) is false. Second, the pattern 0 is matched against
@@ -121,48 +121,51 @@ fact(0) ->
 <input>1</input></pre>
     <p>Evaluation has succeed and <c>m:fact(1)</c> returns 1.</p>
     <p>If <c>m:fact/1</c> is called with a negative number as
-      argument, no clause head will match. A <c>function_clause</c>
-      run-time error will occur.</p>
+      argument, no clause head matches. A <c>function_clause</c>
+      runtime error occurs.</p>
   </section>
 
   <section>
     <title>Tail recursion</title>
     <p>If the last expression of a function body is a function call,
-      a <em>tail recursive</em> 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 <em>tail recursive</em> 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.</p>
-    <p>Example:</p>
+    <p><em>Example:</em></p>
     <pre>
 loop(N) ->
     io:format("~w~n", [N]),
     loop(N+1).</pre>
-    <p>As a counter-example see the factorial example above 
-      that is not tail recursive since a multiplication is done
+    <p>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 <c>fact(N-1)</c>.</p>
   </section>
 
   <section>
-    <title>Built-In Functions, BIFs</title>
-    <p><em>Built-in functions</em>, 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 <c>erlang</c> but there are also built-in functions
+    <title>Built-In Functions (BIFs)</title>
+    <p>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 <c>erlang</c> but there are also BIFs
       belonging to a few other modules, for example <c>lists</c> and
       <c>ets</c>.</p>
-    <p>The most commonly used BIFs belonging to <c>erlang</c> are
-      <em>auto-imported</em>, they do not need to be prefixed with
-      the module name. Which BIFs are auto-imported is specified in
-      <c>erlang(3)</c>. For example, standard type conversion BIFs like
+    <p>The most commonly used BIFs belonging to <c>erlang(3)</c> are
+      <em>auto-imported</em>. They do not need to be prefixed with
+      the module name. Which BIFs that are auto-imported is specified in the
+      <seealso marker="erts:erlang">erlang(3)</seealso> module in ERTS.
+      For example, standard-type conversion BIFs like
       <c>atom_to_list</c> and BIFs allowed in guards can be called
-      without specifying the module name. Examples:</p>
+      without specifying the module name.</p>
+      <p><em>Examples:</em></p>
     <pre>
 1> <input>tuple_size({a,b,c}).</input>
 3
 2> <input>atom_to_list('Erlang').</input>
 "Erlang"</pre>
-    <p>Note that normally it is the set of auto-imported built-in
-      functions that is referred to when talking about 'BIFs'.</p>
+    <p>Notice that it is normally the set of auto-imported BIFs
+      that are referred to when talking about 'BIFs'.</p>
   </section>
 </chapter>