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<div class="titlepage"><div><div><h4 class="title">
<a name="range.reference.utilities.sub_range"></a><a class="link" href="sub_range.html" title="Class sub_range"> Class <code class="computeroutput"><span class="identifier">sub_range</span></code></a>
</h4></div></div></div>
<p>
The <code class="computeroutput"><span class="identifier">sub_range</span></code> class inherits
all its functionality from the <a class="link" href="iterator_range.html" title="Class iterator_range"><code class="computeroutput"><span class="identifier">iterator_range</span></code></a> class. The <code class="computeroutput"><span class="identifier">sub_range</span></code> class is often easier to use
because one must specify the <a class="link" href="../../concepts/forward_range.html" title="Forward Range">Forward
Range</a> template argument instead of an iterator. Moreover, the <code class="computeroutput"><span class="identifier">sub_range</span></code> class can propagate constness
since it knows what a corresponding <code class="computeroutput"><span class="identifier">const_iterator</span></code>
is.
</p>
<a name="range.reference.utilities.sub_range.synopsis"></a><h5>
<a name="id871048"></a>
<a class="link" href="sub_range.html#range.reference.utilities.sub_range.synopsis">Synopsis</a>
</h5>
<p>
</p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span>
<span class="special">{</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">ForwardRange</span> <span class="special">&gt;</span>
<span class="keyword">class</span> <span class="identifier">sub_range</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">iterator_range</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">range_iterator</span><span class="special">&lt;</span><span class="identifier">ForwardRange</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="special">&gt;</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">range_iterator</span><span class="special">&lt;</span><span class="identifier">ForwardRange</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">iterator</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">range_iterator</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="identifier">ForwardRange</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">const_iterator</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">iterator_difference</span><span class="special">&lt;</span><span class="identifier">iterator</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">difference_type</span><span class="special">;</span>
<span class="keyword">public</span><span class="special">:</span> <span class="comment">// construction, assignment
</span> <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">ForwardTraversalIterator</span> <span class="special">&gt;</span>
<span class="identifier">sub_range</span><span class="special">(</span> <span class="identifier">ForwardTraversalIterator</span> <span class="identifier">Begin</span><span class="special">,</span> <span class="identifier">ForwardTraversalIterator</span> <span class="identifier">End</span> <span class="special">);</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">ForwardRange2</span> <span class="special">&gt;</span>
<span class="identifier">sub_range</span><span class="special">(</span> <span class="identifier">ForwardRange2</span><span class="special">&amp;</span> <span class="identifier">r</span> <span class="special">);</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">ForwardRange2</span> <span class="special">&gt;</span>
<span class="identifier">sub_range</span><span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range2</span><span class="special">&amp;</span> <span class="identifier">r</span> <span class="special">);</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">ForwardRange2</span> <span class="special">&gt;</span>
<span class="identifier">sub_range</span><span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">ForwardRange2</span><span class="special">&amp;</span> <span class="identifier">r</span> <span class="special">);</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">ForwardRange2</span> <span class="special">&gt;</span>
<span class="identifier">sub_range</span><span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="keyword">const</span> <span class="identifier">ForwardRange2</span><span class="special">&amp;</span> <span class="identifier">r</span> <span class="special">);</span>
<span class="keyword">public</span><span class="special">:</span> <span class="comment">// Forward Range functions
</span> <span class="identifier">iterator</span> <span class="identifier">begin</span><span class="special">();</span>
<span class="identifier">const_iterator</span> <span class="identifier">begin</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="identifier">iterator</span> <span class="identifier">end</span><span class="special">();</span>
<span class="identifier">const_iterator</span> <span class="identifier">end</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="keyword">public</span><span class="special">:</span> <span class="comment">// convenience
</span> <span class="identifier">value_type</span><span class="special">&amp;</span> <span class="identifier">front</span><span class="special">();</span>
<span class="keyword">const</span> <span class="identifier">value_type</span><span class="special">&amp;</span> <span class="identifier">front</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="identifier">value_type</span><span class="special">&amp;</span> <span class="identifier">back</span><span class="special">();</span>
<span class="keyword">const</span> <span class="identifier">value_type</span><span class="special">&amp;</span> <span class="identifier">back</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span>
<span class="comment">// for Random Access Range only:
</span> <span class="identifier">value_type</span><span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">[](</span> <span class="identifier">size_type</span> <span class="identifier">at</span> <span class="special">);</span>
<span class="keyword">const</span> <span class="identifier">value_type</span><span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">[](</span> <span class="identifier">size_type</span> <span class="identifier">at</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="comment">// rest of interface inherited from iterator_range
</span> <span class="special">};</span>
<span class="special">}</span> <span class="comment">// namespace 'boost'
</span></pre>
<p>
</p>
<p>
The class should be trivial to use as seen below. Imagine that we have
an algorithm that searches for a sub-string in a string. The result is
an iterator_range, that delimits the match. We need to store the result
from this algorithm. Here is an example of how we can do it with and without
<code class="computeroutput"><span class="identifier">sub_range</span></code>
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span><span class="special">(</span><span class="string">"hello"</span><span class="special">);</span>
<span class="identifier">iterator_range</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">::</span><span class="identifier">iterator</span><span class="special">&gt;</span> <span class="identifier">ir</span> <span class="special">=</span> <span class="identifier">find_first</span><span class="special">(</span> <span class="identifier">str</span><span class="special">,</span> <span class="string">"ll"</span> <span class="special">);</span>
<span class="identifier">sub_range</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">sub</span> <span class="special">=</span> <span class="identifier">find_first</span><span class="special">(</span> <span class="identifier">str</span><span class="special">,</span> <span class="string">"ll"</span> <span class="special">);</span>
</pre>
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