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< div class = "section" title = "Class sub_range" >
< 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 >
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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 >
2010-04-28 19:27:44 +00:00
< a name = "id3164631" ></ a >
2010-04-28 16:09:03 +00:00
< a class = "link" href = "sub_range.html#range.reference.utilities.sub_range.synopsis" > Synopsis</ a >
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< 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" > < </ span > < span class = "keyword" > class</ span > < span class = "identifier" > ForwardRange</ span > < span class = "special" > > </ 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" > < </ span > < span class = "keyword" > typename</ span > < span class = "identifier" > range_iterator</ span >< span class = "special" > < </ span >< span class = "identifier" > ForwardRange</ span >< span class = "special" > > ::</ span >< span class = "identifier" > type</ span > < span class = "special" > > </ 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" > < </ span >< span class = "identifier" > ForwardRange</ span >< span class = "special" > > ::</ 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" > < </ span >< span class = "keyword" > const</ span > < span class = "identifier" > ForwardRange</ span >< span class = "special" > > ::</ 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" > < </ span >< span class = "identifier" > iterator</ span >< span class = "special" > > ::</ 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" > < </ span > < span class = "keyword" > class</ span > < span class = "identifier" > ForwardTraversalIterator</ span > < span class = "special" > > </ 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" > < </ span > < span class = "keyword" > class</ span > < span class = "identifier" > ForwardRange2</ span > < span class = "special" > > </ span >
< span class = "identifier" > sub_range</ span >< span class = "special" > (</ span > < span class = "identifier" > ForwardRange2</ span >< span class = "special" > & </ span > < span class = "identifier" > r</ span > < span class = "special" > );</ span >
< span class = "keyword" > template</ span >< span class = "special" > < </ span > < span class = "keyword" > class</ span > < span class = "identifier" > ForwardRange2</ span > < span class = "special" > > </ span >
< span class = "identifier" > sub_range</ span >< span class = "special" > (</ span > < span class = "keyword" > const</ span > < span class = "identifier" > Range2</ span >< span class = "special" > & </ span > < span class = "identifier" > r</ span > < span class = "special" > );</ span >
< span class = "keyword" > template</ span >< span class = "special" > < </ span > < span class = "keyword" > class</ span > < span class = "identifier" > ForwardRange2</ span > < span class = "special" > > </ span >
< span class = "identifier" > sub_range</ span >< span class = "special" > & </ span > < span class = "keyword" > operator</ span >< span class = "special" > =(</ span > < span class = "identifier" > ForwardRange2</ span >< span class = "special" > & </ span > < span class = "identifier" > r</ span > < span class = "special" > );</ span >
< span class = "keyword" > template</ span >< span class = "special" > < </ span > < span class = "keyword" > class</ span > < span class = "identifier" > ForwardRange2</ span > < span class = "special" > > </ span >
< span class = "identifier" > sub_range</ span >< span class = "special" > & </ span > < span class = "keyword" > operator</ span >< span class = "special" > =(</ span > < span class = "keyword" > const</ span > < span class = "identifier" > ForwardRange2</ span >< span class = "special" > & </ 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" > & </ span > < span class = "identifier" > front</ span >< span class = "special" > ();</ span >
< span class = "keyword" > const</ span > < span class = "identifier" > value_type</ span >< span class = "special" > & </ 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" > & </ span > < span class = "identifier" > back</ span >< span class = "special" > ();</ span >
< span class = "keyword" > const</ span > < span class = "identifier" > value_type</ span >< span class = "special" > & </ 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" > & </ 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" > & </ 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 >
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< p >
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< 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" > < </ 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" > > </ 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" > < </ span >< span class = "identifier" > std</ span >< span class = "special" > ::</ span >< span class = "identifier" > string</ span >< span class = "special" > > </ 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 >
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< td align = "right" >< div class = "copyright-footer" > Copyright © 2003 -2010 Thorsten Ottosen, Neil Groves< p >
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at < a href = "http://www.boost.org/LICENSE_1_0.txt" target = "_top" > http://www.boost.org/LICENSE_1_0.txt</ a > )
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