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<p>Executes a for loop over a range.
</p><p>Used as a more readable equivalent to the traditional <a href="for.html" title="cpp/language/for"> for loop</a> operating over a range of values, such as all elements in a container.
</p>
<table id="toc" class="toc"><tr><td><div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="range-for.html#Syntax"><span class="tocnumber">1</span> <span class="toctext">Syntax</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="range-for.html#Explanation"><span class="tocnumber">2</span> <span class="toctext">Explanation</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="range-for.html#Notes"><span class="tocnumber">3</span> <span class="toctext">Notes</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="range-for.html#Keywords"><span class="tocnumber">4</span> <span class="toctext">Keywords</span></a></li>
<li class="toclevel-1 tocsection-5"><a href="range-for.html#Example"><span class="tocnumber">5</span> <span class="toctext">Example</span></a></li>
<li class="toclevel-1 tocsection-6"><a href="range-for.html#See_also"><span class="tocnumber">6</span> <span class="toctext">See also</span></a></li>
</ul>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/range-for&action=edit&section=1" title="Edit section: Syntax">edit</a>]</span> <span class="mw-headline" id="Syntax">Syntax</span></h3>
<table class="t-sdsc-begin">
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td class="t-sdsc-nopad"> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <code><b>for (</b></code> <span class="t-spar">range_declaration</span> <code><b>:</b></code> <span class="t-spar">range_expression</span> <code><b>)</b></code> <span class="t-spar">loop_statement</span>
</td>
<td class="t-sdsc-nopad">
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<table class="t-par-begin">
<tr class="t-par">
<td> <span class="t-spar">attr</span><span class="t-mark-rev t-since-cxx11">(C++11)</span>
</td>
<td> -
</td>
<td> any number of <a href="attributes.html" title="cpp/language/attributes">attributes</a>
</td></tr>
<tr class="t-par">
<td> <span class="t-spar">range_declaration</span>
</td>
<td> -
</td>
<td> a <a href="declarations.html" title="cpp/language/declarations">declaration</a> of a named variable, whose type is the type of the element of the sequence represented by <span class="t-spar">range_expression</span>, or a reference to that type. Often uses the <a href="auto.html" title="cpp/language/auto">auto specifier</a> for automatic type deduction
</td></tr>
<tr class="t-par">
<td> <span class="t-spar">range_expression</span>
</td>
<td> -
</td>
<td> any <a href="expressions.html" title="cpp/language/expressions">expression</a> that represents a suitable sequence (either an array or an object for which <code>begin</code> and <code>end</code> member functions or free functions are defined, see below) or a <a href="list_initialization.html" title="cpp/language/list initialization">braced-init-list</a>.
</td></tr>
<tr class="t-par">
<td> <span class="t-spar">loop_statement</span>
</td>
<td> -
</td>
<td> any <a href="statements.html" title="cpp/language/statements">statement</a>, typically a compound statement, which is the body of the loop
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/range-for&action=edit&section=2" title="Edit section: Explanation">edit</a>]</span> <span class="mw-headline" id="Explanation">Explanation</span></h3>
<p>The above syntax produces code similar to the following (<b><code>__range</code></b>, <b><code>__begin</code></b> and <b><code>__end</code></b> are for exposition only):
</p>
<table class="t-sdsc-begin">
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td class="t-sdsc-nopad"> <code><b>{</b></code><br />
<dl><dd><code><b>auto && __range =</b></code> <span class="t-spar">range_expression</span> <code><b>;</b></code> <br />
</dd><dd><code><b>for (auto __begin =</b></code> <i>begin_expr</i><code><b>,</b></code><br />
<dl><dd><dl><dd><dl><dd><code><b>__end =</b></code> <i>end_expr</i><code><b>;</b></code> <br />
</dd></dl>
</dd><dd><code><b>__begin != __end; ++__begin) {</b></code> <br />
</dd></dl>
</dd><dd><span class="t-spar">range_declaration</span> <code><b>= *__begin;</b></code> <br />
</dd><dd><span class="t-spar">loop_statement</span> <br />
</dd></dl>
</dd><dd><code><b>} </b></code> <br />
</dd></dl>
<p><code><b>} </b></code> <br />
</p>
</td>
<td class="t-sdsc-nopad">
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<p><span class="t-spar">range_expression</span> is evaluated to determine the sequence or range to iterate. Each element of the sequence, in turn, is dereferenced and assigned to the variable with the type and name given in <span class="t-spar">range_declaration</span>.
</p><p><i><code>begin_expr</code></i> and <i><code>end_expr</code></i> are defined as follows:
</p>
<ul><li> If <span class="t-spar">range_expression</span> is an expression of array type, then <i><code>begin_expr</code></i> is <span class="t-c"><span class="mw-geshi cpp source-cpp">__range</span></span> and <i><code>end_expr</code></i> is <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span>__range <span class="sy2">+</span> __bound<span class="br0">)</span></span></span>, where <code>__bound</code> is the number of elements in the array (if the array has unknown size or is of an incomplete type, the program is ill-formed)
</li><li> If <span class="t-spar">range_expression</span> is an expression of a class type <code>C</code> that has a member named <span class="t-c"><span class="mw-geshi cpp source-cpp">begin</span></span> and/or a member named <span class="t-c"><span class="mw-geshi cpp source-cpp">end</span></span>, then <i><code>begin_expr</code></i> is <code>__range.begin()</code> and <i><code>end_expr</code></i> is <code>__range.end()</code>;
</li><li> Otherwise, <i><code>begin_expr</code></i> is <span class="t-c"><span class="mw-geshi cpp source-cpp">begin<span class="br0">(</span>__range<span class="br0">)</span></span></span> and <i><code>end_expr</code></i> is <span class="t-c"><span class="mw-geshi cpp source-cpp">end<span class="br0">(</span>__range<span class="br0">)</span></span></span>, which are found via <a href="adl.html" title="cpp/language/adl">argument-dependent lookup</a> (non-ADL lookup is not performed).
</li></ul>
<p>If <span class="t-spar">range_expression</span> returns a temporary, its lifetime is extended until the end of the loop, as indicated by binding to the rvalue reference <b><code>__range</code></b>, but beware that the lifetime of any temporary within <span class="t-spar">range_expression</span> <i>is not</i> extended.
</p><p>Just as with a traditional loop, a <a href="break.html" title="cpp/language/break"> break statement</a> can be used to exit the loop early and a <a href="continue.html" title="cpp/language/continue"> continue statement</a> can be used to restart the loop with the next element.
</p><p><span class="t-spar">attr</span> represents an optional number of <a href="attributes.html" title="cpp/language/attributes">attributes</a>.
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/range-for&action=edit&section=3" title="Edit section: Notes">edit</a>]</span> <span class="mw-headline" id="Notes">Notes</span></h3>
<p>If the initializer (<span class="t-spar">range_expression</span>) is a braced-init-list, __range is deduced to be <span class="t-lc">std::initializer_list<>&&</span>
</p><p>It is safe, and in fact, preferable in generic code, to use deduction to forwarding reference, <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">for</span><span class="br0">(</span><span class="kw4">auto</span><span class="sy3">&&</span> var <span class="sy4">:</span> sequence<span class="br0">)</span></span></span>.
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/range-for&action=edit&section=4" title="Edit section: Keywords">edit</a>]</span> <span class="mw-headline" id="Keywords">Keywords</span></h3>
<p><a href="../keyword/for.html" title="cpp/keyword/for"><tt>for</tt></a>
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/range-for&action=edit&section=5" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span></h3>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include <iostream></span>
<span class="co2">#include <vector></span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="../container/vector.html"><span class="kw1094">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> v <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span><span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> <span class="sy3">&</span>i <span class="sy4">:</span> v<span class="br0">)</span> <span class="co1">// access by const reference</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> i <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">auto</span> i<span class="sy4">:</span> v<span class="br0">)</span> <span class="co1">// access by value, the type of i is int</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> i <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">auto</span><span class="sy3">&&</span> i<span class="sy4">:</span> v<span class="br0">)</span> <span class="co1">// access by reference, the type of i is int&</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> i <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">int</span> n<span class="sy4">:</span> <span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span><span class="br0">}</span><span class="br0">)</span> <span class="co1">// the initializer may be a braced-init-list</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> n <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
<span class="kw4">int</span> a<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">for</span><span class="br0">(</span><span class="kw4">int</span> n<span class="sy4">:</span> a<span class="br0">)</span> <span class="co1">// the initializer may be an array</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> n <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5</pre></div></div>
</div>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/range-for&action=edit&section=6" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="../algorithm/for_each.html" title="cpp/algorithm/for each"> <span class="t-lines"><span>for_each</span></span></a></div></div>
</td>
<td> applies a function to a range of elements <br /> <span class="t-mark">(function template)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/algorithm/dsc_for_each&action=edit">[edit]</a></span>
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