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diff --git a/system/doc/reference_manual/data_types.xml b/system/doc/reference_manual/data_types.xml index ad92143179..e63825b97d 100644 --- a/system/doc/reference_manual/data_types.xml +++ b/system/doc/reference_manual/data_types.xml @@ -4,20 +4,21 @@ <chapter> <header> <copyright> - <year>2003</year><year>2013</year> + <year>2003</year><year>2015</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> - The contents of this file are subject to the Erlang Public License, - Version 1.1, (the "License"); you may not use this file except in - compliance with the License. You should have received a copy of the - Erlang Public License along with this software. If not, it can be - retrieved online at http://www.erlang.org/. - - Software distributed under the License is distributed on an "AS IS" - basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See - the License for the specific language governing rights and limitations - under the License. + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. </legalnotice> @@ -28,12 +29,12 @@ <rev></rev> <file>data_types.xml</file> </header> + <p>Erlang provides a number of data types, which are listed in + this section.</p> <section> <title>Terms</title> - <p>Erlang provides a number of data types which are listed in this - chapter. A piece of data of any data type is called a - <em>term</em>.</p> + <p>A piece of data of any data type is called a <em>term</em>.</p> </section> <section> @@ -48,13 +49,13 @@ <em><c>char</c></em>.</item> <item><em><c>base</c></em><c>#</c><em><c>value</c></em> <br></br> - Integer with the base <em><c>base</c></em>, which must be an + Integer with the base <em><c>base</c></em>, that must be an integer in the range 2..36. <br></br> In Erlang 5.2/OTP R9B and earlier versions, the allowed range is 2..16.</item> </list> - <p>Examples:</p> + <p><em>Examples:</em></p> <pre> 1> <input>42.</input> 42 @@ -76,11 +77,11 @@ <section> <title>Atom</title> - <p>An atom is a literal, a constant with name. An atom should be + <p>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 @.</p> - <p>Examples:</p> + <p><em>Examples:</em></p> <pre> hello phone_number @@ -91,11 +92,11 @@ phone_number <section> <title>Bit Strings and Binaries</title> <p>A bit string is used to store an area of untyped memory.</p> - <p>Bit Strings are expressed using the + <p>Bit strings are expressed using the <seealso marker="expressions#bit_syntax">bit syntax</seealso>.</p> - <p>Bit Strings which consists of a number of bits which is evenly - divisible by eight are called Binaries</p> - <p>Examples:</p> + <p>Bit strings that consist of a number of bits that are evenly + divisible by eight, are called <em>binaries</em></p> + <p><em>Examples:</em></p> <pre> 1> <input><<10,20>>.</input> <<10,20>> @@ -103,12 +104,14 @@ phone_number <<"ABC">> 1> <input><<1:1,0:1>>.</input> <<2:2>></pre> - <p>More examples can be found in Programming Examples.</p> + <p>For more examples, + see <seealso marker="doc/programming_examples:bit_syntax"> + Programming Examples</seealso>.</p> </section> <section> <title>Reference</title> - <p>A reference is a term which is unique in an Erlang runtime + <p>A reference is a term that is unique in an Erlang runtime system, created by calling <c>make_ref/0</c>.</p> </section> @@ -117,34 +120,42 @@ phone_number <p>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.</p> - <p>Example:</p> + <p><em>Example:</em></p> <pre> 1> <input>Fun1 = fun (X) -> X+1 end.</input> #Fun<erl_eval.6.39074546> 2> <input>Fun1(2).</input> 3</pre> - <p>Read more about funs in <seealso marker="expressions#funs">Fun Expressions</seealso>. More examples can be found in Programming - Examples.</p> + <p>Read more about funs in <seealso marker="expressions#funs"> + Fun Expressions</seealso>. For more examples, see + <seealso marker="doc/programming_examples:funs"> + Programming Examples</seealso>.</p> </section> <section> <title>Port Identifier</title> - <p>A port identifier identifies an Erlang port. <c>open_port/2</c>, - which is used to create ports, will return a value of this type.</p> + <p>A port identifier identifies an Erlang port.</p> + <p><c>open_port/2</c>, which is used to create ports, returns + a value of this data type.</p> <p>Read more about ports in <seealso marker="ports">Ports and Port Drivers</seealso>.</p> </section> <section> <title>Pid</title> - <p>A process identifier, pid, identifies a process. - <c>spawn/1,2,3,4</c>, <c>spawn_link/1,2,3,4</c> and - <c>spawn_opt/4</c>, which are used to create processes, return - values of this type. Example:</p> + <p>A process identifier, pid, identifies a process.</p> + <p>The following BIFs, which are used to create processes, return + values of this data type:</p> + <list type="bulleted"> + <item><c>spawn/1,2,3,4</c></item> + <item><c>spawn_link/1,2,3,4</c></item> + <item><c>spawn_opt/4</c></item> + </list> + <p><em>Example:</em></p> <pre> 1> <input>spawn(m, f, []).</input> <0.51.0></pre> - <p>The BIF <c>self()</c> returns the pid of the calling process. - Example:</p> + <p>In the following example, the BIF <c>self()</c> returns + the pid of the calling process:</p> <pre> -module(m). -export([loop/0]). @@ -167,14 +178,14 @@ who_are_you</pre> <section> <title>Tuple</title> - <p>Compound data type with a fixed number of terms:</p> + <p>A tuple is a compound data type with a fixed number of terms:</p> <pre> {Term1,...,TermN}</pre> <p>Each term <c>Term</c> in the tuple is called an <em>element</em>. The number of elements is said to be the <em>size</em> of the tuple.</p> <p>There exists a number of BIFs to manipulate tuples.</p> - <p>Examples:</p> + <p><em>Examples:</em></p> <pre> 1> <input>P = {adam,24,{july,29}}.</input> {adam,24,{july,29}} @@ -192,7 +203,8 @@ adam <section> <title>Map</title> - <p>Compound data type with a variable number of key-value associations:</p> + <p>A map is a compound data type with a variable number of + key-value associations:</p> <pre> #{Key1=>Value1,...,KeyN=>ValueN}</pre> <p>Each key-value association in the map is called an @@ -200,7 +212,7 @@ adam called <em>elements</em>. The number of association pairs is said to be the <em>size</em> of the map.</p> <p>There exists a number of BIFs to manipulate maps.</p> - <p>Examples:</p> + <p><em>Examples:</em></p> <pre> 1> <input>M1 = #{name=>adam,age=>24,date=>{july,29}}.</input> #{age => 24,date => {july,29},name => adam} @@ -215,16 +227,18 @@ adam 6> <input>map_size(#{}).</input> 0</pre> <p>A collection of maps processing functions can be found in - the STDLIB module <seealso marker="stdlib:maps"><c>maps</c></seealso>.</p> - <p>Read more about <seealso marker="expressions#map_expressions">Maps</seealso>.</p> + <seealso marker="stdlib:maps"><c>maps</c></seealso> manual page + in STDLIB.</p> + <p>Read more about maps in <seealso marker="expressions#map_expressions"> + Map Expressions</seealso>.</p> <note> - <p>Maps are considered experimental during OTP 17.</p> + <p>Maps are considered to be experimental during Erlang/OTP R17.</p> </note> </section> <section> <title>List</title> - <p>Compound data type with a variable number of terms.</p> + <p>A list is a compound data type with a variable number of terms.</p> <pre> [Term1,...,TermN]</pre> <p>Each term <c>Term</c> in the list is called an @@ -232,20 +246,21 @@ adam the <em>length</em> of the list.</p> <p>Formally, a list is either the empty list <c>[]</c> or consists of a <em>head</em> (first element) and a <em>tail</em> - (remainder of the list) which is also a list. The latter can + (remainder of the list). + The <em>tail</em> is also a list. The latter can be expressed as <c>[H|T]</c>. The notation - <c>[Term1,...,TermN]</c> above is actually shorthand for + <c>[Term1,...,TermN]</c> above is equivalent with the list <c>[Term1|[...|[TermN|[]]]]</c>.</p> - <p>Example: <br></br> -<c>[]</c> is a list, thus <br></br> + <p><em>Example:</em></p> +<p><c>[]</c> is a list, thus <br></br> <c>[c|[]]</c> is a list, thus <br></br> <c>[b|[c|[]]]</c> is a list, thus <br></br> -<c>[a|[b|[c|[]]]]</c> is a list, or in short <c>[a,b,c]</c>.</p> - <p></p> +<c>[a|[b|[c|[]]]]</c> is a list, or in short <c>[a,b,c]</c></p> + <p>A list where the tail is a list is sometimes called a <em>proper list</em>. It is allowed to have a list where the tail is not a - list, for example <c>[a|b]</c>. However, this type of list is of + list, for example, <c>[a|b]</c>. However, this type of list is of little practical use.</p> - <p>Examples:</p> + <p><em>Examples:</em></p> <pre> 1> <input>L1 = [a,2,{c,4}].</input> [a,2,{c,4}] @@ -262,18 +277,19 @@ a 7> <input>length([]).</input> 0</pre> <p>A collection of list processing functions can be found in - the STDLIB module <c>lists</c>.</p> + the <seealso marker="stdlib:lists">lists</seealso> manual + page in STDLIB.</p> </section> <section> <title>String</title> <p>Strings are enclosed in double quotes ("), but is not a - data type in Erlang. Instead a string <c>"hello"</c> is - shorthand for the list <c>[$h,$e,$l,$l,$o]</c>, that is + data type in Erlang. Instead, a string <c>"hello"</c> is + shorthand for the list <c>[$h,$e,$l,$l,$o]</c>, that is, <c>[104,101,108,108,111]</c>.</p> <p>Two adjacent string literals are concatenated into one. This is - done at compile-time and does not incur any runtime overhead. - Example:</p> + done in the compilation, thus, does not incur any runtime overhead.</p> + <p><em>Example:</em></p> <pre> "string" "42"</pre> <p>is equivalent to</p> @@ -285,12 +301,13 @@ a <title>Record</title> <p>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 <c>shell(3)</c> - for details.</p> - <p>Examples:</p> + the shell unless special actions are taken. For details, see the + <seealso marker="stdlib:shell">shell(3)</seealso> manual + page in STDLIB).</p> + <p><em>Examples:</em></p> <pre> -module(person). -export([new/2]). @@ -304,14 +321,15 @@ new(Name, Age) -> {person,ernie,44}</pre> <p>Read more about records in <seealso marker="records">Records</seealso>. More examples can be - found in Programming Examples.</p> + found in <seealso marker="doc/programming_examples:records"> + Programming Examples</seealso>.</p> </section> <section> <title>Boolean</title> <p>There is no Boolean data type in Erlang. Instead the atoms <c>true</c> and <c>false</c> are used to denote Boolean values.</p> - <p>Examples:</p> + <p><em>Examples:</em></p> <pre> 1> <input>2 =< 3</input>. true @@ -330,76 +348,80 @@ true</pre> </row> <row> <cell align="left" valign="middle">\b</cell> - <cell align="left" valign="middle">backspace</cell> + <cell align="left" valign="middle">Backspace</cell> </row> <row> <cell align="left" valign="middle">\d</cell> - <cell align="left" valign="middle">delete</cell> + <cell align="left" valign="middle">Delete</cell> </row> <row> <cell align="left" valign="middle">\e</cell> - <cell align="left" valign="middle">escape</cell> + <cell align="left" valign="middle">Escape</cell> </row> <row> <cell align="left" valign="middle">\f</cell> - <cell align="left" valign="middle">form feed</cell> + <cell align="left" valign="middle">Form feed</cell> </row> <row> <cell align="left" valign="middle">\n</cell> - <cell align="left" valign="middle">newline</cell> + <cell align="left" valign="middle">Newline</cell> </row> <row> <cell align="left" valign="middle">\r</cell> - <cell align="left" valign="middle">carriage return</cell> + <cell align="left" valign="middle">Carriage return</cell> </row> <row> <cell align="left" valign="middle">\s</cell> - <cell align="left" valign="middle">space</cell> + <cell align="left" valign="middle">Space</cell> </row> <row> <cell align="left" valign="middle">\t</cell> - <cell align="left" valign="middle">tab</cell> + <cell align="left" valign="middle">Tab</cell> </row> <row> <cell align="left" valign="middle">\v</cell> - <cell align="left" valign="middle">vertical tab</cell> + <cell align="left" valign="middle">Vertical tab</cell> </row> <row> <cell align="left" valign="middle">\XYZ, \YZ, \Z</cell> - <cell align="left" valign="middle">character with octal representation XYZ, YZ or Z</cell> + <cell align="left" valign="middle">Character with octal + representation XYZ, YZ or Z</cell> </row> <row> <cell align="left" valign="middle">\xXY</cell> - <cell align="left" valign="middle">character with hexadecimal representation XY</cell> + <cell align="left" valign="middle">Character with hexadecimal + representation XY</cell> </row> <row> <cell align="left" valign="middle">\x{X...}</cell> - <cell align="left" valign="middle">character with hexadecimal representation; X... is one or more hexadecimal characters</cell> + <cell align="left" valign="middle">Character with hexadecimal + representation; X... is one or more hexadecimal characters</cell> </row> <row> <cell align="left" valign="middle">\^a...\^z <br></br> \^A...\^Z</cell> - <cell align="left" valign="middle">control A to control Z</cell> + <cell align="left" valign="middle">Control A to control Z</cell> </row> <row> <cell align="left" valign="middle">\'</cell> - <cell align="left" valign="middle">single quote</cell> + <cell align="left" valign="middle">Single quote</cell> </row> <row> <cell align="left" valign="middle">\"</cell> - <cell align="left" valign="middle">double quote</cell> + <cell align="left" valign="middle">Double quote</cell> </row> <row> <cell align="left" valign="middle">\\</cell> - <cell align="left" valign="middle">backslash</cell> + <cell align="left" valign="middle">Backslash</cell> </row> - <tcaption>Recognized Escape Sequences.</tcaption> + <tcaption>Recognized Escape Sequences</tcaption> </table> </section> <section> <title>Type Conversions</title> - <p>There are a number of BIFs for type conversions. Examples:</p> + <p>There are a number of BIFs for type conversions.</p> + <p><em>Examples:</em></p> <pre> 1> <input>atom_to_list(hello).</input> "hello" |