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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Boost.Assignment Documentation </title>
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body>
<table border="0" >
<tr>
<td ><img src="../../../boost.png" border="0" ></td>
<td >
<h1 align="center">Assignment Library</h1>
</td>
</tr>
</table>
<p>
Copyright 2003-2004 Thorsten Ottosen
</p>
<p>
Use, modification and distribution is subject to the Boost Software License, Version 1.0
(see <a href=http://www.boost.org/LICENSE_1_0.txt>
http://www.boost.org/LICENSE_1_0.txt</a>).
</p>
<h3>Table of Contents</h3>
<ul>
<li><a href="#intro">Introduction</a></li>
<li>
<a href="#tutorial" >Tutorial</a>
<ul>
<li>Function <a href="#operator+="><code>operator+=()</code></a>
<li>Function <a href="#operator()"><code>operator()()</code></a>
<li>Function <a href="#list_of"><code>list_of()</code></a>
<li>Function <a href="#map_list_of"><code>map_list_of()</code></a>
<li>Functions <a href="#repeat"><code>repeat()</code> and <code>repeat_fun()</code> </a>
<li>A <a href="#complicated">"complicated"</a> example
</ul>
<li>
<a href="#reference">Reference</a>
<ul>
<li><a href="#headers">Headers</a> </li>
<li><a href="#std">Standard containers</a> </li>
<li>Functions <a href="#list_of_ref"><code>list_of()</code> and <code>map_list_of()</code></a></li>
<li>Functions <a href="#repeat_ref"><code>repeat()</code> and <code>repeat_fun()</code> </a>
<li>Class <a href="#list_inserter"><code>list_inserter</code></a></li>
<li>Function <a href="#make_list_inserter"><code>make_list_inserter()</code></a></li>
<li><a href="#limit"> Customizing</a> argument list sizes</li>
</ul>
<li> <a href="#exceptions">Exceptions and exception-safety </a></li>
<li> <a href="#extensions">Extending the library</a>
<li> <a href="#boost_libs">Supported libraries </a>
<li> <a href="#examples">Examples</a></li> <ul></ul>
<li><a href="#portability">Portability</a></li>
<li><a href="#history">History and Acknowledgment</a>
<li><a href="#ref">References</a></li>
</ul>
<hr>
<h2><a name="intro">Introduction</a></h2> <p> <i>There appear to be few
practical uses of <code>operator,()</code></i>. <!-- p. 247 --> <br><b>Bjarne
Stroustrup</b>, The Design and Evolution of C++ </p> <p> The purpose of this
library is to make it easy to fill containers with data by overloading
<code>operator,()</code> and <code>operator()()</code>. These two operators
makes it possible to construct lists of values which are then copied into a
container: </p> <ul> <li> A comma-separated list: <p>
<!-- vector< int > v; v += 1,2,3,4,5,6,7,8,9; -->
<pre><span
class=identifier>vector</span><span class=special><</span><span
class=keyword>int</span><span class=special>></span><span
class=identifier> v</span><span class=special>; </span>
<span class=identifier>v </span><span class=special>+= </span><span
class=number>1</span><span
class=special>,</span><span class=number>2</span><span
class=special>,</span><span class=number>3</span><span
class=special>,</span><span class=number>4</span><span
class=special>,</span><span class=number>5</span><span
class=special>,</span><span class=number>6</span><span
class=special>,</span><span class=number>7</span><span
class=special>,</span><span class=number>8</span><span
class=special>,</span><span class=number>9</span><span class=special>;</span></pre></p>
<li> A parenthesis-separated list:
<p>
<pre>
<span class=identifier>map</span><span class=special><</span><span
class=identifier>string</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>m</span><span class=special>; </span>
<span class=identifier>insert</span><span class=special>( </span><span class=identifier>m </span><span class=special>)( </span><span class=string>"Bar"</span><span class=special>, </span><span class=number>1 </span><span class=special>)( </span><span class=string>"Foo"</span><span class=special>, </span><span class=number>2 </span><span class=special>);</span></pre>
</ul>
<p>
These lists are particularly useful in
learning, testing, and prototyping situations, but can also be handy otherwise.
The library comes with predefined operators for the containers of the
standard library, but most functionality will work with any standard
compliant container. The library also makes it possible to extend user
defined types so for example a member function can be called for a list of
values instead of its normal arguments. </p>
<hr>
<a name="tutorial"></a>
<h2>Tutorial</h2>
<p>
Within two minutes you should be able to use this library. The main
components are explained in these sections:
<ul>
<li>Function <a href="#operator+="><code>operator+=()</code></a>
<li>Function <a href="#operator()"><code>operator()()</code></a>
<li>Function <a href="#list_of"><code>list_of()</code></a>
<li>Function <a href="#map_list_of"><code>map_list_of()</code></a>
<li>Functions <a href="#repeat"><code>repeat()</code> and <code>repeat_fun()</code> </a>
<li>A <a href="#complicated">"complicated"</a> example
</ul>
The two first functions are used for adding elements after a container object
has been created whereas the next two is used when we need to initialize an
object. </p>
<h3>Function <code>operator+=()</code><a name="operator+="></h3>
<p>
To fill a vector (or any standard container) with values using
<code>operator+=()</code> you write
<blockquote><pre>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>std</span><span class=special>/</span><span class=identifier>vector</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>> </span><span class=comment>// for 'operator+=()'
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>; </span><span class=comment>// bring 'operator+=()' into scope
</span><span class=special>
</span><span class=special>{
</span><span class=identifier>vector</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>values</span><span class=special>;
</span><span class=identifier>values </span><span class=special>+= </span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>,</span><span class=number>4</span><span class=special>,</span><span class=number>5</span><span class=special>,</span><span class=number>6</span><span class=special>,</span><span class=number>7</span><span class=special>,</span><span class=number>8</span><span class=special>,</span><span class=number>9</span><span class=special>; </span><span class=comment>// insert values at the end of the container
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>values</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>9 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>values</span><span class=special>[</span><span class=number>0</span><span class=special>] </span><span class=special>== </span><span class=number>1 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>values</span><span class=special>[</span><span class=number>9</span><span class=special>] </span><span class=special>== </span><span class=number>9 </span><span class=special>);
</span><span class=special>}</span></pre></blockquote>
Here we only stuffed constants into the container, but the list can
consists of arbitrary expressions as long as the result of each
expression is convertible to the <code>value_type</code> of the container.
</p>
<h3>Function <code>operator()()</code> <a name="operator()"></h3>
<p>
We do not call <code>operator()()</code> directly, but instead we call a
function that returns a proxy-object that defines <code>operator()()</code>.
The function that returns the proxy object is always named after the member
function that is used to copy the values in the list into the container.
So to fill a map with pairs of values you write
<blockquote><pre>
<span class=preprocessor>#include </span><span class=special><</span><span
class=identifier>boost</span><span class=special>/</span><span
class=identifier>assign</span><span class=special>/</span><span
class=identifier>list_inserter</span><span class=special>.</span><span
class=identifier>hpp</span><span class=special>> </span><span class=comment>// for 'insert()'
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>string</span><span class=special>>
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>; </span><span class=comment>// bring 'insert()' into scope
</span><span class=special>
</span><span class=special>{
</span><span class=identifier>map</span><span class=special><</span><span class=identifier>string</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>months</span><span class=special>;
</span><span class=identifier>insert</span><span class=special>( </span><span class=identifier>months </span><span class=special>)
</span><span class=special>( </span><span class=string>"january"</span><span class=special>, </span><span class=number>31 </span><span class=special>)( </span><span class=string>"february"</span><span class=special>, </span><span class=number>28 </span><span class=special>)
</span><span class=special>( </span><span class=string>"march"</span><span class=special>, </span><span class=number>31 </span><span class=special>)( </span><span class=string>"april"</span><span class=special>, </span><span class=number>30 </span><span class=special>)
</span><span class=special>( </span><span class=string>"may"</span><span class=special>, </span><span class=number>31 </span><span class=special>)( </span><span class=string>"june"</span><span class=special>, </span><span class=number>30 </span><span class=special>)
</span><span class=special>( </span><span class=string>"july"</span><span class=special>, </span><span class=number>31 </span><span class=special>)( </span><span class=string>"august"</span><span class=special>, </span><span class=number>31 </span><span class=special>)
</span><span class=special>( </span><span class=string>"september"</span><span class=special>, </span><span class=number>30 </span><span class=special>)( </span><span class=string>"october"</span><span class=special>, </span><span class=number>31 </span><span class=special>)
</span><span class=special>( </span><span class=string>"november"</span><span class=special>, </span><span class=number>30 </span><span class=special>)( </span><span class=string>"december"</span><span class=special>, </span><span class=number>31 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>m</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>12 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>m</span><span class=special>[</span><span class=string>"january"</span><span class=special>] </span><span class=special>== </span><span class=number>31 </span><span class=special>);
</span><span class=special>}</span> </pre></blockquote>
Note that <code>operator()()</code> is much more handy when
we need to construct objects using several arguments
(up to five arguments are supported by default, but the limit can be <a href="#limit">customized</a>).
This is also true for sequences:
<blockquote><pre>
<span class=preprocessor>#include </span><span class=special><</span><span
class=identifier>boost</span><span class=special>/</span><span
class=identifier>assign</span><span class=special>/</span>list_inserter</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>> </span><span class=comment>// for 'push_front()'
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>string</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>utility</span><span class=special>>
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>; </span><span class=comment>// bring 'push_front()' into scope
</span><span class=special>
</span><span class=special>{
</span><span class=keyword>typedef </span><span class=identifier>pair</span><span class=special>< </span><span class=identifier>string</span><span class=special>,</span><span class=identifier>string </span><span class=special>> </span><span class=identifier>str_pair</span><span class=special>;
</span><span class=identifier>deque</span><span class=special><</span><span class=identifier>str_pair</span><span class=special>> </span><span class=identifier>deq</span><span class=special>;
</span><span class=identifier>push_front</span><span class=special>( </span><span class=identifier>deq </span><span class=special>)( </span><span class=string>"foo"</span><span class=special>, </span><span class=string>"bar"</span><span class=special>)( </span><span class=string>"boo"</span><span class=special>, </span><span class=string>"far" </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>deq</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>2 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>deq</span><span class=special>.</span><span class=identifier>front</span><span class=special>().</span><span class=identifier>first </span><span class=special>== </span><span class=string>"boo" </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>deq</span><span class=special>.</span><span class=identifier>back</span><span class=special>().</span><span class=identifier>second </span><span class=special>== </span><span class=string>"bar" </span><span class=special>);
</span><span class=special>} </span></pre></blockquote>
Besides <code>push_front()</code> we could also have used
<code>push_back()</code> if the container has a corresponding member
function. Empty parentheses can be used to insert default-constructed
objects, for example,
<code>push_front( deq )()()</code> will insert two default-constructed
<code>str_pair</code> objects. </p>
<p>
If <code>operator()()</code> is too cumbersome to use with eg.
<code>push_front()</code>we can also say </p>
<blockquote>
<pre>
<span class=identifier>deque</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>di</span><span class=special>; </span>
<span class=identifier>push_front</span><span class=special>( </span><span class=identifier>di </span><span class=special>) </span><span class=special>= </span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>,</span><span class=number>4</span><span class=special>,</span><span class=number>5</span><span class=special>,</span><span class=number>6</span><span class=special>,</span><span class=number>7</span><span class=special>,</span><span class=number>8</span><span class=special>,</span><span class=number>9</span><span class=special>;</span>
<span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>di</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>9 </span><span class=special>); </span>
<span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>di</span><span class=special>[</span><span class=number>8</span><span class=special>] </span><span class=special>== </span><span class=number>9 </span><span class=special>); </span>
</pre>
</blockquote>
<p>
Just to make it perfectly clear, the code above is not restricted to the
standard containers, but will work with all <i>standard compliant</i> containers
with the right member function. It is only <code>operator+=()</code> that has been restricted to
the standard containers. </p>
<h3>Function <code>list_of()</code> <a name="list_of"></h3>
But what if we need to <i>initialize</i> a container? This is where
<code>list_of()</code> comes into play. With <code>list_of()</code>
we can create anonymous lists that automatically converts to
any container:
<blockquote><pre>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>list_of</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>> </span><span class=comment>// for 'list_of()'
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>list</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>stack</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>string</span><span class=special>>
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>; </span><span class=comment>// bring 'list_of()' into scope
</span><span class=special>
</span><span class=special>{
</span><span class=keyword>const </span><span class=identifier>list</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>primes </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>)(</span><span class=number>5</span><span class=special>)(</span><span class=number>7</span><span class=special>)(</span><span class=number>11</span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>primes</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>6 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>primes</span><span class=special>.</span><span class=identifier>back</span><span class=special>() </span><span class=special>== </span><span class=number>11 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>primes</span><span class=special>.</span><span class=identifier>front</span><span class=special>() </span><span class=special>== </span><span class=number>1 </span><span class=special>);
</span><span class=keyword>const </span><span
class=identifier>stack</span><span class=special><</span><span
class=identifier>string</span><span class=special>> </span><span
class=identifier>names </span><span class=special>= </span><span
class=special></span><span class=identifier>list_of</span><span class=special>( </span><span class=string>"Mr. Foo" </span><span class=special>)( </span><span class=string>"Mr. Bar"</span><span class=special>)( </span><span class=string>"Mrs. FooBar" </span><span
class=special>).</span><span class=identifier>to_adapter();
</span><span class=keyword>const </span><span
class=identifier>stack</span><span class=special><</span><span
class=identifier>string</span><span class=special>> </span><span
class=identifier>names2 </span><span class=special>= </span><span
class=special>(</span><span class=identifier>list_of</span><span class=special>( </span><span class=string>"Mr. Foo" </span><span class=special>), </span><span class=string>"Mr. Bar"</span><span class=special>, </span><span class=string>"Mrs. FooBar" </span><span
class=special>).</span><span class=identifier>to_adapter();
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>names</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>3 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>names</span><span class=special>[</span><span class=number>0</span><span class=special>] </span><span class=special>== </span><span class=string>"Mr. Foo" </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>names</span><span class=special>[</span><span class=number>2</span><span class=special>] </span><span class=special>== </span><span class=string>"Mrs. FooBar" </span><span class=special>);
</span><span class=special>} </span></pre></blockquote>
If we need to initialize a container adapter, we need to help the compiler a
little by calling <code>to_adapter()</code>. As the second example also shows,
we can use a comma-separated
list with <code>list_of()</code> if we add parenthesis around the
entire right hand side. It is worth noticing that the first argument
of <code>list_of()</code> determines the type of the anonymous list.
In case of the stack, the anonymous list consists of
<code>const char*</code> objects which are then converted to
a stack of <code>string</code> objects. The conversion is always
possible as long as the conversion between the stored types is possible.
</p>
<p>
Please notice that <code>list_of()</code> can even convert to a
<code>boost::<a
href="../../array/index.html">array</a><T,sz></code> and see also the list
of <a href="#boost_libs">supported libraries </a>.
<h3>Function <code>map_list_of()</code> <a name="map_list_of"></h3>
This function is defined for pure convenience when working with
maps. Its usage is simple:
<blockquote><pre>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>list_of</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>> </span><span class=comment>// for 'map_list_of()'
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>map</span><span class=special>>
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>; </span><span class=comment>// bring 'map_list_of()' into scope
</span><span class=special>
</span><span class=special>{
</span><span class=identifier>map</span><span class=special><</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>next </span><span class=special>= </span><span class=identifier>map_list_of</span><span class=special>(</span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>)(</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>)(</span><span class=number>3</span><span class=special>,</span><span class=number>4</span><span class=special>)(</span><span class=number>4</span><span class=special>,</span><span class=number>5</span><span class=special>)(</span><span class=number>5</span><span class=special>,</span><span class=number>6</span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>next</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>5 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>next</span><span class=special>[ </span><span class=number>1 </span><span class=special>] </span><span class=special>== </span><span class=number>2 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>next</span><span class=special>[ </span><span class=number>5 </span><span class=special>] </span><span class=special>== </span><span class=number>6 </span><span class=special>);
</span><span class=comment>// or we can use 'list_of()' by specifying what type
// the list consists of
</span><span class=identifier>next </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>< </span><span class=identifier>pair</span><span class=special><</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=special>>(</span><span class=number>6</span><span class=special>,</span><span class=number>7</span><span class=special>)(</span><span class=number>7</span><span class=special>,</span><span class=number>8</span><span class=special>)(</span><span class=number>8</span><span class=special>,</span><span class=number>9</span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>next</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>3 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>next</span><span class=special>[ </span><span class=number>6 </span><span class=special>] </span><span class=special>== </span><span class=number>7 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>next</span><span class=special>[ </span><span class=number>8 </span><span class=special>] </span><span class=special>== </span><span class=number>9 </span><span class=special>);
</span><span class=special>} </span></pre></blockquote>
<h3>Functions <code>repeat()</code> and <code>repeat_fun()</code> <a name="repeat"></h3>
<p>
Sometimes it is too irritating to repeat the same value many times. This is
where <code>repeat()</code> can be handy:
<blockquote>
<pre>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>list_of</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>std</span><span class=special>/</span><span class=identifier>vector</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
</span>
<span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;</span>
<span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>;</span>
<span class=special> </span>
<span class=special>{
</span><span class=identifier>vector</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>v</span><span class=special>;
</span><span class=identifier>v </span><span class=special>+= </span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>,</span><span class=identifier>repeat</span><span class=special>(</span><span class=number>10</span><span class=special>,</span><span class=number>4</span><span class=special>),</span><span class=number>5</span><span class=special>,</span><span class=number>6</span><span class=special>,</span><span class=number>7</span><span class=special>,</span><span class=number>8</span><span class=special>,</span><span class=number>9</span><span class=special>;
</span><span class=comment>// v = [1,2,3,4,4,4,4,4,4,4,4,4,4,5,6,7,8,9]
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>3 </span><span class=special>+ </span><span class=number>10 </span><span class=special>+ </span><span class=number>5 </span><span class=special>);
</span><span class=identifier>v </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>).</span><span class=identifier>repeat</span><span class=special>(</span><span class=number>5</span><span class=special>,</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>);
</span><span class=comment>// v = [1,2,2,2,2,2,3]
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>1 </span><span class=special>+ </span><span class=number>5 </span><span class=special>+ </span><span class=number>1 </span><span class=special>);
</span><span class=identifier>push_back</span><span class=special>( </span><span class=identifier>v </span><span class=special>)(</span><span class=number>1</span><span class=special>).</span><span class=identifier>repeat</span><span class=special>(</span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>);
</span><span class=comment>// v = old v + [1,2,3]
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>10 </span><span class=special>);</span>
<span class=special>}</span></pre>
</blockquote>
As we can see, then the first argument to <code>repeat()</code> is the number
of times to repeat the second argument.
</p>
<p>
A more general list can be constructed with <code>repeat_fun()</code>:
<blockquote>
<pre>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>std</span><span class=special>/</span><span class=identifier>vector</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>cstdlib</span><span class=special>> </span><span class=comment>// for 'rand()'
</span>
<span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;</span>
<span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>;</span>
<span class=special> </span>
<span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T </span><span class=special>></span>
<span class=keyword>struct </span><span class=identifier>next </span>
<span class=special>{
</span><span class=identifier>T </span><span class=identifier>seed</span><span class=special>;
</span><span class=identifier>next</span><span class=special>( </span><span class=identifier>T </span><span class=identifier>seed </span><span class=special>) </span><span class=special>: </span><span class=identifier>seed</span><span class=special>(</span><span class=identifier>seed</span><span class=special>)
</span><span class=special>{ </span><span class=special>}
</span><span class=identifier>T </span><span class=keyword>operator</span><span class=special>()() </span><span class=keyword>const
</span><span class=special>{
</span><span class=keyword>return </span><span class=identifier>seed</span><span class=special>++;
</span><span class=special>}</span>
<span class=special>};</span>
<span class=special> </span>
<span class=special>{
</span><span class=identifier>vector</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>v</span><span class=special>;
</span><span class=identifier>v </span><span class=special>+= </span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>,</span><span class=identifier>repeat_fun</span><span class=special>(</span><span class=number>4</span><span class=special>,&</span><span class=identifier>rand</span><span class=special>),</span><span class=number>4</span><span class=special>;
</span><span class=comment>// v = [1,2,?,?,?,?,4]
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>7 </span><span class=special>);
</span><span class=identifier>push_back</span><span class=special>( </span><span class=identifier>v </span><span class=special>).</span><span class=identifier>repeat_fun</span><span class=special>(</span><span class=number>4</span><span class=special>,</span><span class=identifier>next</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=number>0</span><span class=special>))(</span><span class=number>4</span><span class=special>).</span><span class=identifier>repeat_fun</span><span class=special>(</span><span class=number>4</span><span class=special>,</span><span class=identifier>next</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=number>5</span><span class=special>));
</span><span class=comment>// v = old v + [0,1,2,3,4,5,6,7,8]
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>16 </span><span class=special>);</span>
<span class=special>}</span> </pre>
</blockquote>
The only requirement of the second argument to <code>repeat_fun()</code> is that
it is a nullary function. </p>
<h3>A "complicated" example <a name="complicated"></h3>
<p>
As a last example, let us assume that we need to keep track of the
result of soccer matches. A team will get one point if it wins
and zero otherwise. If there has been played three games in each group, the code might look
like this:
<blockquote>
<pre>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>/</span><span class=identifier>list_of</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span
class=identifier>boost</span><span class=special>/</span><span
class=identifier>assign</span><span class=special>/</span><span
class=identifier>list_inserter</span><span class=special>.</span><span
class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>string</span><span class=special>></span>
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>vector</span><span class=special>>
</span>
<span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;</span>
<span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>;
</span>
<span class=special>{
</span><span class=keyword>typedef </span><span class=identifier>vector</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>score_type</span><span class=special>;
</span><span class=keyword>typedef </span><span class=identifier>map</span><span class=special><</span><span class=identifier>string</span><span class=special>,</span><span class=identifier>score_type</span><span class=special>> </span><span class=identifier>team_score_map</span><span class=special>;
</span><span class=keyword>typedef </span><span class=identifier>pair</span><span class=special><</span><span class=identifier>string</span><span class=special>,</span><span class=identifier>score_type</span><span class=special>> </span><span class=identifier>score_pair</span><span class=special>;
</span><span class=identifier>team_score_map </span><span class=identifier>group1</span><span class=special>, </span><span class=identifier>group2</span><span class=special>;
</span><span class=comment>//
// method 1: using 'insert()'
//
</span><span class=identifier>insert</span><span class=special>( </span><span class=identifier>group1 </span><span class=special>)( </span><span class=string>"Denmark"</span><span class=special>, </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>1</span><span class=special>) </span><span class=special>)
</span><span class=special>( </span><span class=string>"Germany"</span><span class=special>, </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>0</span><span class=special>)(</span><span class=number>0</span><span class=special>) </span><span class=special>)
</span><span class=special>( </span><span class=string>"England"</span><span class=special>, </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>0</span><span class=special>)(</span><span class=number>1</span><span class=special>) </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>group1</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>3 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>group1</span><span class=special>[ </span><span class=string>"Denmark" </span><span class=special>][</span><span class=number>1</span><span class=special>] </span><span class=special>== </span><span class=number>1 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>group1</span><span class=special>[ </span><span class=string>"Germany" </span><span class=special>][</span><span class=number>0</span><span class=special>] </span><span class=special>== </span><span class=number>0 </span><span class=special>);
</span><span class=comment>//
// method 2: using 'list_of()'
//
</span><span class=identifier>group2 </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>< </span><span class=identifier>score_pair </span><span class=special>>
</span><span class=special>( </span><span class=string>"Norway"</span><span class=special>, </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>0</span><span class=special>) </span><span class=special>)
</span><span class=special>( </span><span class=string>"USA"</span><span class=special>, </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>0</span><span class=special>)(</span><span class=number>0</span><span class=special>) </span><span class=special>)
</span><span class=special>( </span><span class=string>"Andorra"</span><span class=special>, </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>1</span><span class=special>) </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>group2</span><span class=special>.</span><span class=identifier>size</span><span class=special>() </span><span class=special>== </span><span class=number>3 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>group2</span><span class=special>[ </span><span class=string>"Norway" </span><span class=special>][</span><span class=number>0</span><span class=special>] </span><span class=special>== </span><span class=number>1 </span><span class=special>);
</span><span class=identifier>BOOST_ASSERT</span><span class=special>( </span><span class=identifier>group2</span><span class=special>[ </span><span class=string>"USA" </span><span class=special>][</span><span class=number>0</span><span class=special>] </span><span class=special>== </span><span class=number>0 </span><span class=special>);</span>
<span class=special>}</span>
</pre>
</blockquote>
In the first example, notice how the result of <code>list_of()</code>
can be converted automatically to a <code>vector<int></code> because
<code>insert()</code> knows it expects a <code>vector<int></code>.
In the second example we can see that <code>list_of()</code> is somewhat
less intelligent since here it needs to be told explicitly what arguments to
expect. (In the future it might be possible to introduce a more intelligent
conversion layer in <code>list_of()</code>.)
</p>
</p>
That is all; now you are ready to use this library.
</p>
<hr>
<h2><a name="reference">Reference</a></h2>
<p>
It is worth noticing the way the library is implemented.
A free-standing function (eg. <code>push_back()</code>
or <code>operator+=()</code>) returns a proxy
object which is responsible for the insertion or the assignment. The proxy
object does the insertion or assignment by overloading <code>operator,()</code>
and <code>operator()()</code> and by calling the "insert" function from within
those operators. The "insert" function is typically stored in the proxy object
by using <code>boost::<a href="../../function/index.html">function</a></code>. </p>
<p>
Often overloading
of <code>operator,()</code> is discouraged because it can lead to surprising
results, but the approach taken in this library is safe since the
user never deals with objects that have overloaded <code>operator,()</code>
directly. However, you should be aware of this:
</p>
<p><i>
The
expressions in a comma-separated list no longer follow the rules of the
built-in comma-operator. This means that the order of evaluation of
expressions in a comma-separated list is undefined like when one specifies
a list of function arguments.
</i></p>
<p>
Most of the code in this document use <code>int</code> in the examples,
but of course it works for arbitrary types as long as they are
Copy Constructible. The inserted data need not be constant data,
but can be variables or data returned from functions; the only requirement
is that the type of the data is convertible to the type stored in the
container.
</p>
<p>
All forwarding is done by passing objects by value. Originally
<code>const</code> references was used, but it lead to many problems
with string-literals. One thing to remember is that references
can be passed by using <code>boost::<a href=http://www.boost.org/doc/html/ref.html>ref</a></code>.
</p>
<p>
Everything is put in namespace
<code>boost::assign</code>. </p>
<p> More details can be found below: </p>
<ul>
<li><a href="#headers">Headers</a> </li>
<li><a href="#std">Standard containers</a> </li>
<li>Functions <a href="#list_of_ref"><code>list_of()</code> and <code>map_list_of()</code></a></li>
<li>Functions <a href="#repeat_ref"><code>repeat()</code> and <code>repeat_fun()</code></a></li>
<li>Class <a href="#list_inserter"><code>list_inserter</code></a></li>
<li>Function <a href="#make_list_inserter"><code>make_list_inserter()</code></a></li>
<li><a href="#limit">Customizing</a> argument list sizes </li>
</ul>
<h3>Headers <a name="headers"></h3>
<p>
An overview of the headers in this library
is given below. Please notice <code><boost/assign/list_inserter.hpp></code>
is included for each header that defines <code>operator+=()</code>.</p>
<table cellpadding=5 border=1 > <tr>
<th> Header </th>
<th> Includes </th>
<tr>
<td> <boost/assign.hpp> </td>
<td> everything </td>
<tr>
<td> <boost/assign/list_of.hpp> </td>
<td> <a href="#list_of"><code>list_of()</a>, <a
href="#map_list_of">map_list_of()</code></a> </td> <tr>
<td> <boost/assign/std.hpp> </td>
<td> <a href="#operator+="><code>operator+=()</code></a> for all
standard
containers (see below)</td> <tr> <td> <boost/assign/std/deque.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::deque</code>, <code><deque></code>
<tr>
<td> <boost/assign/std/list.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::list</code>, <code><list></code>
<tr>
<td> <boost/assign/std/map.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::map</code> and <code>std::multimap</code> ,
<code><map></code> <tr>
<td> <boost/assign/std/queue.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::queue</code> and <code>std::priority_queue</code>,
<code><queue></code> <tr>
<td> <boost/assign/std/set.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::set</code> and <code>std::multiset</code>,
<code><set></code> <tr>
<td> <boost/assign/std/slist.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::slist</code> if the class is available ,
<code><slist></code> <tr>
<td> <boost/assign/std/stack.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::stack</code>, <code><stack></code>
<tr>
<td> <boost/assign/std/vector.hpp> </td>
<td> <code>operator+=()</code> for
<code>std::vector</code>, <code><vector></code>
<tr>
<td> <boost/assign/assignment_exception.hpp> </td>
<td> Class <a
href="#assignment_exception"><code>assignment_exception</code></a> which might
be thrown by the proxy returned by <code>list_of()</code>
<tr>
<td> <boost/assign/list_inserter.hpp> </td>
<td>Functions <a
href="#make_list_inserter"><code>make_list_inserter()</code></a>, <code>push_back()</code>,
<code>push_front()</code>,<code>insert()</code>,
<code>
push()</code> and class <a href="#list_inserter"><code>list_inserter</code></a>
which is the back-bone of this entire library.
</table>
<h3>Standard containers <a name="std"> </h3>
<p> In the following three dots (...) will mean
implementation defined.
<code>operator+=()</code> returns a proxy that forwards calls to either
<code>push_back()</code>,<code>insert()</code>, or <code>push()</code>
depending on which operation the container supports. </p> <b>Synopsis</b>
<p>
<blockquote>
<pre>
<span class=keyword>namespace </span><span class=identifier>boost</span>
<span class=special>{</span>
<span class=keyword>namespace </span><span class=identifier>assign</span>
<span class=special>{
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>deque</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>list</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>K</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>P </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>map</span><span class=special><</span><span class=identifier>K</span><span class=special>,</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>C</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>m</span><span class=special>, </span><span class=keyword>const </span><span class=identifier>P</span><span class=special>& </span><span class=identifier>p </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>K</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>P </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>multimap</span><span class=special><</span><span class=identifier>K</span><span class=special>,</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>C</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>m</span><span class=special>, </span><span class=keyword>const </span><span class=identifier>P</span><span class=special>& </span><span class=identifier>p </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>queue</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>C</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>priority_queue</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>C</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>K</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>K2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>set</span><span class=special><</span><span class=identifier>K</span><span class=special>,</span><span class=identifier>C</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>K2 </span><span class=identifier>k </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>K</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>K2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>multiset</span><span class=special><</span><span class=identifier>K</span><span class=special>,</span><span class=identifier>C</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>K2 </span><span class=identifier>k </span><span class=special>);
</span><span class=preprocessor>#ifdef </span><span class=identifier>BOOST_HAS_SLIST
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>slist</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>);
</span><span class=preprocessor>#endif
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>C</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>stack</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>C</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>); </span>
<span class=special>} </span><span class=comment>// namespace 'assign'</span>
<span class=special>} </span><span class=comment>// namespace 'boost'</span> </pre></blockquote>
Note that the extra template argument <code>V2</code> etc. is
necessary to allow for types convertible to <code>V</code>.
<h3>Functions <code>list_of()</code> and
<code>map_list_of()</code> <a name=list_of_ref> </h3>
<p>
These two functions are used to construct anonymous
list which can be converted to any standard container
and <code>boost::<a href=../../array/index.html>array</a><T,sz>.</code>
The object returned by the two
functions is guaranteed to have the interface described below.
</p>
<b>Synopsis</b>
<blockquote>
<pre><span class=keyword>namespace </span><span class=identifier>boost </span>
<span class=special>{</span>
<span class=keyword>namespace </span><span class=identifier>assign</span>
<span class=special>{
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T </span><span class=special>>
</span><span class=keyword>class </span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span>
</span><span class=special>{
</span><span class=keyword>public</span><span class=special>:
</span><span class=identifier>const_iterator </span><span class=identifier>begin</span><span class=special>() <span class=keyword>const</span>;
</span><span class=identifier>const_iterator </span><span class=identifier>end</span><span class=special>() <span class=keyword>const</span>;
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span>& </span><span class=keyword>operator</span><span class=special>,( </span><span class=identifier>U </span><span class=identifier>u </span><span class=special>);
</span><span class=comment>// inserts default-constructed object
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span>& </span><span class=keyword>operator</span><span class=special>()();
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span>& </span><span class=keyword>operator</span><span class=special>()( </span><span class=identifier>U </span><span class=identifier>u </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U2 </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span>& </span><span class=keyword>operator</span><span class=special>()( </span><span class=identifier>U </span><span class=identifier>u</span><span class=special>, </span><span class=identifier>U2 </span><span class=identifier>u2 </span><span class=special>);
</span><span class=comment>//
// and similarly up to 5 arguments
//
//
// Convert to a 'Container'. 'Container' must have a constructor
// which takes two iterators.
//
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>Container </span><span class=special>>
</span><span class=keyword>operator </span><span class=identifier>Container</span><span class=special>() </span><span class=keyword>const</span><span class=special>;
</span><span class=comment>//
// Convert to a container adapter like 'std::stack<>'.
//
</span><span class=identifier>Convertible</span><span class=special>-</span><span class=identifier>to</span><span class=special>-</span><span class=identifier>adapter</span> </span><span class=identifier>to_adapter</span><span class=special>() </span><span class=keyword>const</span><span class=special>;
</span><span class=comment>//
//
// Convert to eg. 'boost::array<T,std::size_t>'. If the
// assigned variable is too small,
// a <a href="#assignment_exception">assignment_exception</a> is thrown.
// If the assigned variable it is too big, the rest of the
// values are default-constructed.
//
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>template </span><span class=special><</span><span class=keyword>class</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span><span class=special>> </span><span class=keyword>class </span><span class=identifier>Array</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t </span><span class=identifier>sz </span><span class=special>>
</span><span class=keyword>operator </span><span class=identifier>Array</span><span class=special><</span><span class=identifier>U</span><span class=special>,</span><span class=identifier>sz</span><span class=special>>() </span><span class=keyword>const</span><span class=special>;
</span><span class=special>};
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>list_of</span><span class=special>(</span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>list_of</span><span class=special>( </span><span class=identifier>T </span><span class=identifier>t </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U2 </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>list_of</span><span class=special>( </span><span class=identifier>U </span><span class=identifier>u</span><span class=special>, </span><span class=identifier>U2 </span><span class=identifier>u2 </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U2</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U3 </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>list_of</span><span class=special>( </span><span class=identifier>U </span><span class=identifier>u</span><span class=special>, </span><span class=identifier>U2 </span><span class=identifier>u2</span><span class=special>, </span><span class=identifier>U3 </span><span class=identifier>u3 </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U2</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U3</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U4 </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>list_of</span><span class=special>( </span><span class=identifier>U </span><span class=identifier>u</span><span class=special>, </span><span class=identifier>U2 </span><span class=identifier>u2</span><span class=special>, </span><span class=identifier>U3 </span><span class=identifier>u3</span><span class=special>, </span><span class=identifier>U4 </span><span class=identifier>u4 </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U2</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U3</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U4</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U5 </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>list_of</span><span class=special>( </span><span class=identifier>U </span><span class=identifier>u</span><span class=special>, </span><span class=identifier>U2 </span><span class=identifier>u2</span><span class=special>, </span><span class=identifier>U3 </span><span class=identifier>u3</span><span class=special>, </span><span class=identifier>U4 </span><span class=identifier>u4</span><span class=special>, </span><span class=identifier>U5 </span><span class=identifier>u5 </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>Key</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>T </span><span class=special>>
</span><span class=identifier>Implementation</span><span class=special>-</span><span class=identifier>defined</span> </span><span class=identifier>map_list_of</span><span class=special>( </span><span class=identifier>Key </span><span class=identifier>k</span><span class=special>, </span><span class=identifier>T </span><span class=identifier>t </span><span class=special>)
</span><span class=special>{
</span><span class=keyword>return </span><span class=identifier>list_of</span><span class=special>< </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>pair</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>> </span><span class=special>>()( </span><span class=identifier>k</span><span class=special>, </span><span class=identifier>t </span><span class=special>);
</span><span class=special>}</span>
<span class=special>} </span><span class=comment>// namespace 'assign'</span>
<span class=special>} </span><span class=comment>// namespace 'boost'</span> </pre></blockquote>
<h3>Functions <code>repeat()</code> and
<code>repeat_fun()</code> <a name="repeat_ref"> </h3>
<p>
These two function exist both as free-standing functions and as member functions of the object returned by
<code>list_of()</code> and of <code>list_inserter</code>. The free-standing versions are used to create a
hook for <code>operator,()</code> so we can call the functions in the middle of a comma-list. The member functions
are used when we need to call the functions in the middle of a parenthesis-list. In both cases we have that
<ul>
<li> the return type is always implementation defined for both functions,
<li> the argument list of <code>repeat()</code> is <code>(std::size_t,T)</code>, and
<li> the argument list of <code>repeat_fun()</code> is <code>(std::size_t,Nullary_function)</code>
</ul>
</p>
<h3><a name="list_inserter">Class <code>list_inserter</code></a></h3>
This class is responsible for inserting elements into containers and
it is the key to extending the library to support your favourite class.
<p>
<b>Synopsis</b>
</p>
<blockquote><pre>
<span class=keyword>namespace </span><span class=identifier>boost</span>
<span class=special>{</span>
<span class=keyword>namespace </span><span class=identifier>assign</span>
<span class=special>{
</span><span class=keyword>template</span><span class=special>< </span><span class=identifier>Function</span><span class=special>, </span><span class=identifier>Argument </span><span class=special>= </span><span class=keyword>void </span><span class=special>>
</span><span class=keyword>class </span><span class=identifier>list_inserter
</span><span class=special>{
</span><span class=identifier>Function </span><span class=identifier>fun</span><span class=special>;
</span><span class=keyword>public</span><span class=special>:
</span><span class=keyword>explicit </span><span class=identifier>list_inserter</span><span class=special>( </span><span class=identifier>Function </span><span class=identifier>fun </span><span class=special>);
</span><span class=comment>// conversion constructor
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>Function2</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>Arg </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>( </span><span class=keyword>const </span><span class=identifier>list_inserter</span><span class=special><</span><span class=identifier>Function2</span><span class=special>,</span><span class=identifier>Arg</span><span class=special>>& </span><span class=special>);
</span><span class=keyword>public</span><span class=special>:
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>& </span><span class=keyword>operator</span><span class=special>,( </span><span class=identifier>U </span><span class=identifier>u </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>& </span><span class=keyword>operator</span><span class=special>=( </span><span class=identifier>U </span><span class=identifier>u </span><span class=special>);
</span><span class=comment>// calls 'fun()' with default-constructed object
</span><span class=identifier>list_inserter</span><span class=special>& </span><span class=keyword>operator</span><span class=special>()();
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>& </span><span class=keyword>operator</span><span class=special>()( </span><span class=identifier>U </span><span class=identifier>u </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>U</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>U2 </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>& </span><span class=keyword>operator</span><span class=special>()( </span><span class=identifier>U </span><span class=identifier>u</span><span class=special>, </span><span class=identifier>U2 </span><span class=identifier>u2 </span><span class=special>)
</span><span class=special>{
</span><span class=comment>//
// if 'Argument' is 'void'
// fun( u, u2 );
// else
// fun( Argument( u, u2 ) );
//
</span><span class=keyword>return </span><span class=special>*</span><span class=keyword>this</span><span class=special>;
</span><span class=special>}
</span><span class=comment>//
// similarly up to 5 arguments
//
</span><span class=special>};</span>
<span class=keyword>template</span><span class=special>< </span><span
class=keyword>class </span><span class=identifier>C </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=identifier>push_back</span><span class=special>( </span><span class=identifier>C</span><span class=special>& </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>C </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=identifier>push_front</span><span class=special>( </span><span class=identifier>C</span><span class=special>& </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>C </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=identifier>insert</span><span class=special>( </span><span class=identifier>C</span><span class=special>& </span><span class=special>);
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>C </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=special>... </span><span class=special>> </span><span class=identifier>push</span><span class=special>( </span><span class=identifier>C</span><span class=special>& </span><span class=special>);</span>
<span class=special>} </span><span class=comment>// namespace 'assign'</span>
<span class=special>} </span><span class=comment>// namespace 'boost'</span></pre></blockquote>
<p>
Notice how the arguments to <code>operator,()</code> and
<code>operator()()</code> are passed differently to
<code>fun</code> depending of the type of <code>Argument</code>.
So if we only pass one template argument to <code>list_inserter,</code>
we can forward "arbitrary" argument lists of functions. If we pass
two template arguments to <code>list_inserter</code> we can
construct types with "arbitrary" constructors.
</p>
<p>
And because
a reference to <code>list_inserter</code> is returned, we can
chain argument list together in a very space-efficient manner.
</p>
<h3><a name="make_list_inserter">Function <code>make_list_inserter()</code></a></h3>
<p>
A simple "constructor" function for <code>list_inserter</code>. A typical
use of this function is to call it with the result of
<code>boost::bind()</code>
which in general returns some unreadable and weird class template.
</p>
<b>Synopsis</b>
<blockquote><pre>
<span class=keyword>namespace </span><span class=identifier>boost </span>
<span class=special>{</span>
<span class=keyword>namespace </span><span class=identifier>assign</span>
<span class=special>{
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>Function </span><span class=special>>
</span><span class=identifier>list_inserter</span><span class=special><</span><span class=identifier>Function</span><span class=special>> </span><span class=identifier>make_list_inserter</span><span class=special>( </span><span class=identifier>Function </span><span class=identifier>fun </span><span class=special>)
</span><span class=special>{
</span><span class=keyword>return </span><span class=identifier>list_inserter</span><span class=special><</span><span class=identifier>Function</span><span class=special>>( </span><span class=identifier>fun </span><span class=special>);
</span><span class=special>} </span>
<span class=special>}</span>
<span class=special>} </span> </pre></blockquote>
<a name="limit"></a>
<h3>Customizing argument list sizes</h3>
<p>
This library uses the boost Preprocessor Library to implement overloaded
versions of <code>operator()()</code> and <code>list_of()</code>. By default you
can call these functions with five arguments, but you can also customize this
number by defining a macros before including a header from this library:
<blockquote>
<pre>
<span class=preprocessor>#define </span><span class=identifier>BOOST_ASSIGN_MAX_PARAMS </span><span class=number>10
</span><span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assign</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
</pre>
</blockquote>
</p>
<hr>
<h2><a name="exceptions">Exceptions and exception-safety</a></h2>
<p>
The exception guarantees by the library is the same as guarantee as the
guarantee of the function that is forwarded to. For standard
containers this means that the
strong guarantee is given for a single insertions and that the basic guarantee
is given for many insertions (provided that the object being copied
gives the basic guarantee).
</p>
<p>
The functions may throw standard exceptions
like <code>std::bad_alloc</code>. Note however that, unfortunately, the standard does not guarantee allocation-failures
in standard containers to be reported by <code>std::bad_alloc</code> or exceptions derived from <code>std::exception</code>.
</p>
<h3><a name="assignment_exception">Class
<code>assignment_exception</code></a></h3>
<p>
The exception is thrown by the conversion operator in the proxy object
returned from <code>list_of()</code>.
</p>
<blockquote><pre>
<span class=keyword>namespace </span><span class=identifier>boost </span>
<span class=special>{</span>
<span class=keyword>namespace </span><span class=identifier>assign</span>
<span class=special>{
</span><span class=keyword>class </span><span class=identifier>assignment_exception </span><span class=special>: </span><span class=keyword>public </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>exception
</span><span class=special>{
</span><span class=keyword>public</span><span class=special>:
</span><span class=keyword>explicit </span><span class=identifier>assignment_exception</span><span class=special>( </span><span class=keyword>const </span><span class=keyword>char</span><span class=special>* </span><span class=identifier>what </span><span class=special>);
</span><span class=keyword>virtual </span><span class=keyword>const </span><span class=keyword>char</span><span class=special>* </span><span class=identifier>what</span><span class=special>() </span><span class=keyword>const </span><span class=keyword>throw</span><span class=special>();
</span><span class=special>};</span>
<span class=special>} </span>
<span class=special>}</span> </pre></blockquote>
<hr>
<h2><a name="extensions">Extending the library</a></h2>
<p>
It is very simple to make the library work with new classes.
This code shows how to use <code>operator+=()</code> with
a container:
<blockquote><pre>
<span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>V</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>A</span><span class=special>, </span><span class=keyword>class </span><span class=identifier>V2 </span><span class=special>>
</span><span class=keyword>inline </span><span class=identifier>list_inserter</span><span class=special>< </span><span class=identifier>assign_detail</span><span class=special>::</span><span class=identifier>call_push_back</span><span class=special>< </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>> </span><span class=special>>, </span><span class=identifier>V </span><span class=special>>
</span><span class=keyword>operator</span><span class=special>+=( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>>& </span><span class=identifier>c</span><span class=special>, </span><span class=identifier>V2 </span><span class=identifier>v </span><span class=special>)
</span><span class=special>{
</span><span class=keyword>return </span><span class=identifier>make_list_inserter</span><span class=special>( </span><span class=identifier>assign_detail</span><span class=special>::</span><span class=identifier>call_push_back</span><span class=special>< </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>V</span><span class=special>,</span><span class=identifier>A</span><span class=special>> </span><span class=special>>( </span><span class=identifier>c </span><span class=special>) </span><span class=special>)( </span><span class=identifier>v </span><span class=special>);
</span><span class=special>}
</span></pre>
</blockquote>
where <code>call_push_back</code> is defined as
<blockquote>
<pre>
<span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>C </span><span class=special>>
</span><span class=keyword>class </span><span class=identifier>call_push_back
</span><span class=special>{
</span><span class=identifier>C</span><span class=special>& </span><span class=identifier>c_</span><span class=special>;
</span><span class=keyword>public</span><span class=special>:
</span><span class=identifier>call_push_back</span><span class=special>( </span><span class=identifier>C</span><span class=special>& </span><span class=identifier>c </span><span class=special>) </span><span class=special>: </span><span class=identifier>c_</span><span class=special>( </span><span class=identifier>c </span><span class=special>)
</span><span class=special>{ </span><span class=special>}
</span><span class=keyword>template</span><span class=special>< </span><span class=keyword>class </span><span class=identifier>T </span><span class=special>>
</span><span class=keyword>void </span><span class=keyword>operator</span><span class=special>()( </span><span class=identifier>T </span><span class=identifier>r </span><span class=special>)
</span><span class=special>{
</span><span class=identifier>c_</span><span class=special>.</span><span class=identifier>push_back</span><span class=special>( </span><span class=identifier>r </span><span class=special>);
</span><span class=special>}
</span><span class=special>};</span></pre>
</blockquote>
Note that we pass
a second template argument to <code>list_inserter</code> so argument
lists will be used to construct a <code>V</code> object. Otherwise we
could end up trying to call <code>push_back()</code> with <i>n</i> arguments
instead of one.
</p>
<p>
An alternative way would be to use <code>boost::function</code> and
<code>boost::bind()</code> in combination. However, in this case one must
remember that it is illegal to take the address of a function in
the standard library.
</p>
<p>
Calling a function with more that one argument can be
very useful too. This small example shows how we take advantage of this
functionality:
</p>
<blockquote><pre>
<span class=comment>//
// A class representing emails
//</span>
<span class=keyword>class </span><span class=identifier>email</span>
<span class=special>{</span>
<span class=keyword>public</span><span class=special>:
</span><span class=keyword>enum </span><span class=identifier>address_option
</span><span class=special>{
</span><span class=identifier>check_addr_book</span><span class=special>,
</span><span class=identifier>dont_check_addr_book
</span><span class=special>};
</span>
<span class=keyword>private</span><span class=special>:
</span><span class=keyword>typedef </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>map</span><span class=special>< </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,</span><span class=identifier>address_option </span><span class=special>> </span><span class=identifier>address_map</span><span class=special>;
</span><span class=comment>//
// Store list of persons that must be cc'ed
//
</span><span class=keyword>mutable </span><span class=identifier>address_map </span><span class=identifier>cc_list</span><span class=special>;
</span><span class=comment>//
// This extra function-object will take care of the
// insertion for us. It stores a reference to a
// map and 'operator()()' does the work.
//
</span><span class=keyword>struct </span><span class=identifier>add_to_map
</span><span class=special>{
</span><span class=identifier>address_map</span><span class=special>& </span><span class=identifier>m</span><span class=special>;
</span><span class=identifier>add_to_map</span><span class=special>( </span><span class=identifier>address_map</span><span class=special>& </span><span class=identifier>m </span><span class=special>) </span><span class=special>: </span><span class=identifier>m</span><span class=special>(</span><span class=identifier>m</span><span class=special>)
</span><span class=special>{}
</span><span class=keyword>void </span><span class=keyword>operator</span><span class=special>()( </span><span class=keyword>const </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>& </span><span class=identifier>name</span><span class=special>, </span><span class=identifier>address_option </span><span class=identifier>ao </span><span class=special>)
</span><span class=special>{
</span><span class=identifier>m</span><span class=special>[ </span><span class=identifier>name </span><span class=special>] </span><span class=special>= </span><span class=identifier>ao</span><span class=special>;
</span><span class=special>}
</span><span class=special>};
</span>
<span class=keyword>public</span><span class=special>:
</span><span class=comment>//
// This function constructs the appropriate 'list_inserter'.
// Again we could have use 'boost::function', but it is
// trivial to use a function object.
//
// Notice that we do not specify an extra template
// parameter to 'list_inserter'; this means we forward
// all parameters directly to the function without
// calling any constructor.
//
</span><span class=identifier>list_inserter</span><span class=special>< </span><span class=identifier>add_to_map </span><span class=special>>
</span><span class=identifier>add_cc</span><span class=special>( </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>name</span><span class=special>, </span><span class=identifier>address_option </span><span class=identifier>ao </span><span class=special>)
</span><span class=special>{
</span><span class=comment>//
// Notice how we pass the arguments 'name' and 'ao' to
// the 'list_inserter'.
//
</span><span class=keyword>return </span><span class=identifier>make_list_inserter</span><span class=special>( </span><span class=identifier>add_to_map</span><span class=special>( </span><span class=identifier>cc_list </span><span class=special>) </span><span class=special>)( </span><span class=identifier>name</span><span class=special>, </span><span class=identifier>ao </span><span class=special>);
</span><span class=special>}</span>
<span class=special>};
</span>
<span class=comment>//
// Now we can use the class like this:
//</span>
<span class=identifier>email </span><span class=identifier>e</span><span class=special>;</span>
<span class=identifier>e</span><span class=special>.</span><span class=identifier>add_cc</span><span class=special>( </span><span class=string>"Mr. Foo"</span><span class=special>, </span><span class=identifier>email</span><span class=special>::</span><span class=identifier>dont_check_addr_book </span><span class=special>)
</span><span class=special>( </span><span class=string>"Mr. Bar"</span><span class=special>, </span><span class=identifier>email</span><span class=special>::</span><span class=identifier>check_addr_book </span><span class=special>)
</span><span class=special>( </span><span class=string>"Mrs. FooBar"</span><span class=special>, </span><span class=identifier>email</span><span class=special>::</span><span class=identifier>check_addr_book </span><span class=special>); </span>
</pre></blockquote>
The full example can be seen in <a href="email_example.html">email_example.cpp</a> </p>
<hr>
<h2>Examples <a name="examples"></h2>
<p>
Additional examples can be found in the test files:
<ul>
<li> <a href="email_example.html">email_example.cpp</a>
<li> <a href="my_vector_example.html">my_vector_example.cpp</a>
<li> <a href="multi_index_container.html">multi_index_container.cpp</a>
<li> <a href="../test/array.cpp">array.cpp</a>
<li> <a href="../test/list_of.cpp">list_of.cpp</a>
<li> <a href="../test/std.cpp">std.cpp</a>
<li> <a href="../test/list_inserter.cpp">list_inserter.cpp</a>
<li> <a href="../test/list_of_workaround.cpp">list_of_work_around.cpp</a>
</ul> </p>
<hr>
<h2><a name="boost_libs">Supported libraries</a></h2>
Here is a list libraries has been tested with Boost.Assign:
<ol>
<li> <code>boost::<a href=../../array/index.html>array</a></code>
<li> <code>boost::<a href=../../multi_index/index.html>multi_index_container</a></code>
</ol>
<p>
</p>
<hr>
<h2><a name="portability">Portability</a></h2>
<p>
Library has been successfully compiled and tested with
MVC++ 7.1, GCC 3.2 (under Cygwin) Comeau 4.3.3
</p>
<p>
There are known limitation on platforms not supporting templated
conversion operators. The solution is to call certain member functions on
the object returned by <code>list_of()</code>: </p>
<blockquote>
<pre>
<span class=special>{
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>std</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>;
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>assign</span><span class=special>;
</span><span class=keyword></span><span
class=identifier>vector</span><span
class=special><</span><span class=keyword>int</span><span
class=special>></span> <span class=identifier>v </span><span
class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>)(</span><span class=number>4</span><span class=special>).</span><span class=identifier>to_container</span><span class=special>( </span><span class=identifier>v </span><span class=special>);
</span><span class=identifier>set</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>s </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>)(</span><span class=number>4</span><span class=special>).</span><span class=identifier>to_container</span><span class=special>( </span><span class=identifier>s </span><span class=special>);
</span><span class=identifier>map</span><span class=special><</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>m </span><span class=special>= </span><span class=identifier>map_list_of</span><span class=special>(</span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>)(</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>).</span><span class=identifier>to_container</span><span class=special>( </span><span class=identifier>m </span><span class=special>);
</span><span class=identifier>stack</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>st </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>)(</span><span class=number>4</span><span class=special>).</span><span class=identifier>to_adapter</span><span class=special>( </span><span class=identifier>st </span><span class=special>);
</span><span class=identifier>queue</span><span class=special><</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>q </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>)(</span><span class=number>4</span><span class=special>).</span><span class=identifier>to_adapter</span><span class=special>( </span><span class=identifier>q </span><span class=special>);
</span><span class=identifier>array</span><span class=special><</span><span class=keyword>int</span><span class=special>,</span><span class=number>4</span><span class=special>> </span><span class=identifier>a </span><span class=special>= </span><span class=identifier>list_of</span><span class=special>(</span><span class=number>1</span><span class=special>)(</span><span class=number>2</span><span class=special>)(</span><span class=number>3</span><span class=special>)(</span><span class=number>4</span><span class=special>).</span><span class=identifier>to_array</span><span class=special>( </span><span class=identifier>a </span><span class=special>);</span>
<span class=special>}</span> </pre>
</blockquote>
<p>
Notice how one must supply the functions with an argument so the right
return type can be deduced.
</p>
<p>Some standard libraries are also broken. One problem is that
<code>insert()</code> might not work:
<blockquote>
<pre>
<span class=identifier>map</span><span class=special><</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>next</span><span class=special>;
</span><span class=identifier>insert</span><span class=special>( </span><span class=identifier>next </span><span class=special>)(</span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>)(</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>); </span><span class=comment>// compile-time error</span> </pre>
</blockquote>
The solution is to use <code>map_list_of()</code> instead:
<blockquote>
<pre>
<span class=identifier>map</span><span class=special><</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>int</span><span class=special>> </span><span class=identifier>next </span><span class=special>= </span><span class=identifier>map_list_of</span><span class=special>(</span><span class=number>1</span><span class=special>,</span><span class=number>2</span><span class=special>)(</span><span class=number>2</span><span class=special>,</span><span class=number>3</span><span class=special>);</span></pre></blockquote>
</p>
<hr>
<h2><a name="history">History and Acknowledgment</a></h2>
<p>
The idea for an assignment/initialization library is not new. The
functionality of this
library resembles Leor Zolman's STL Container Initialization Library a great
deal, but it does not rely on string parsing to achieve its goals.
</p>
<p>
The
library is non-intrusive and puts only a minimum of requirements
on its supported classes.
Overloading operator comma is sometimes viewed as a bad practice <a
href=#meyers>[1]</A>. However, it has been done
with success in eg. the Generative Matrix Computation Library and Blitz to initialize matrices
(see <a href=#gmcl>[2]</A>) and <a href=#blitz>[3]</A>). The
Initialization Library overloads
the comma operator in a safe manner by letting free standing functions
return an object that is responsible for the initialization. Therefore it takes
explicit
action from the programmer to begin using the overloaded <code>operator,()</CODE>.
</p>
<p>
There has recently been some discussion about enhancing the language to
support better initialization (see <a href="#initializer">[4]</a>).
</p>
<p>
Special thanks goes to
<ul>
<li> Leor Zolman for our many discussion that eventually led to this library.
<li> Tom Brinkman for being review manager.
<li> Joaqun Muoz for vc6/vc7 portability.
<li> Pavel Vozenilek for his countless suggestions, improvements and
portability fixes.
</ul>
</p>
<hr>
<h2><a name="ref">References</a></h2>
<p>
<ol>
<li> <a name="meyers"> Scott. Meyers, "More Effective C++", Item 7, Addison Wesley, 1996
<li> <a name="gmcl"> K. Czarnecki and U.W. Eisenecker, "Generative programming", Addison-Wesley, 2000
<li> <a name="blitz"> <a href=http://www.oonumerics.org/blitz/> http://www.oonumerics.org/blitz/ </A>
<li> <a name="initializer">
Gabriel Dos Reis and Bjarne Stroustrup,
<a href=http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1509.pdf> "Generalized Initializer
Lists"</a>, 2003 </a>
</OL>
</p>
<hr>
<p>
(C) Copyright Thorsten Ottosen 2003-2004
</p>
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