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< title > Method 2: provide free-standing functions and specialize metafunctions< / title >
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< div class = "section" title = "Method 2: provide free-standing functions and specialize metafunctions" >
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< a name = "range.reference.extending.method_2" > < / a > < a class = "link" href = "method_2.html" title = "Method 2: provide free-standing functions and specialize metafunctions" > Method 2: provide
free-standing functions and specialize metafunctions< / a >
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< p >
This procedure assumes that you cannot (or do not wish to) change the types
that should be made conformant to a Range concept. If this is not true,
see < a class = "link" href = "method_1.html" title = "Method 1: provide member functions and nested types" > method 1< / a > .
< / p >
< p >
The primary templates in this library are implemented such that certain
functions are found via argument-dependent-lookup (ADL). Below is given
an overview of which free-standing functions a class must specify to be
useable as a certain Range concept. Let < code class = "computeroutput" > < span class = "identifier" > x< / span > < / code >
be a variable (< code class = "computeroutput" > < span class = "keyword" > const< / span > < / code > or < code class = "computeroutput" > < span class = "keyword" > mutable< / span > < / code > ) of the class in question.
< / p >
< div class = "informaltable" > < table class = "table" >
< colgroup >
< col >
< col >
< / colgroup >
< thead > < tr >
< th >
< p >
Function
< / p >
< / th >
< th >
< p >
Related concept
< / p >
< / th >
< / tr > < / thead >
< tbody >
< tr >
< td >
< p >
< code class = "computeroutput" > < span class = "identifier" > range_begin< / span > < span class = "special" > (< / span > < span class = "identifier" > x< / span > < span class = "special" > )< / span > < / code >
< / p >
< / td >
< td >
< p >
< a class = "link" href = "../../concepts/single_pass_range.html" title = "Single Pass Range" > Single Pass
Range< / a >
< / p >
< / td >
< / tr >
< tr >
< td >
< p >
< code class = "computeroutput" > < span class = "identifier" > range_end< / span > < span class = "special" > (< / span > < span class = "identifier" > x< / span > < span class = "special" > )< / span > < / code >
< / p >
< / td >
< td >
< p >
< a class = "link" href = "../../concepts/single_pass_range.html" title = "Single Pass Range" > Single Pass
Range< / a >
< / p >
< / td >
< / tr >
< / tbody >
< / table > < / div >
< p >
< code class = "computeroutput" > < span class = "identifier" > range_begin< / span > < span class = "special" > ()< / span > < / code >
and < code class = "computeroutput" > < span class = "identifier" > range_end< / span > < span class = "special" > ()< / span > < / code >
must be overloaded for both < code class = "computeroutput" > < span class = "keyword" > const< / span > < / code >
and < code class = "computeroutput" > < span class = "keyword" > mutable< / span > < / code > reference arguments.
< / p >
< p >
You must also specialize two metafunctions for your type < code class = "computeroutput" > < span class = "identifier" > X< / span > < / code > :
< / p >
< div class = "informaltable" > < table class = "table" >
< colgroup >
< col >
< col >
< / colgroup >
< thead > < tr >
< th >
< p >
Metafunction
< / p >
< / th >
< th >
< p >
Related concept
< / p >
< / th >
< / tr > < / thead >
< tbody >
< tr >
< td >
< p >
< code class = "computeroutput" > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > range_mutable_iterator< / span > < / code >
< / p >
< / td >
< td >
< p >
< a class = "link" href = "../../concepts/single_pass_range.html" title = "Single Pass Range" > Single Pass
Range< / a >
< / p >
< / td >
< / tr >
< tr >
< td >
< p >
< code class = "computeroutput" > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > range_const_iterator< / span > < / code >
< / p >
< / td >
< td >
< p >
< a class = "link" href = "../../concepts/single_pass_range.html" title = "Single Pass Range" > Single Pass
Range< / a >
< / p >
< / td >
< / tr >
< / tbody >
< / table > < / div >
< p >
A complete example is given here:
< / p >
< p >
< / p >
< pre class = "programlisting" > < span class = "preprocessor" > #include< / span > < span class = "special" > < < / span > < span class = "identifier" > boost< / span > < span class = "special" > /< / span > < span class = "identifier" > range< / 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" > iterator< / span > < span class = "special" > > < / span > < span class = "comment" > // for std::iterator_traits, std::distance()
< / span >
< span class = "keyword" > namespace< / span > < span class = "identifier" > Foo< / span >
< span class = "special" > {< / span >
< span class = "comment" > //
< / span > < span class = "comment" > // Our sample UDT. A 'Pair'
< / span > < span class = "comment" > // will work as a range when the stored
< / span > < span class = "comment" > // elements are iterators.
< / span > < span class = "comment" > //
< / 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" > Pair< / span >
< span class = "special" > {< / span >
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< span class = "identifier" > T< / span > < span class = "identifier" > first< / span > < span class = "special" > ,< / span > < span class = "identifier" > last< / span > < span class = "special" > ;< / span >
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< span class = "special" > };< / span >
< span class = "special" > }< / span > < span class = "comment" > // namespace 'Foo'
< / span >
< span class = "keyword" > namespace< / span > < span class = "identifier" > boost< / span >
< span class = "special" > {< / span >
< span class = "comment" > //
< / span > < span class = "comment" > // Specialize metafunctions. We must include the range.hpp header.
< / span > < span class = "comment" > // We must open the 'boost' namespace.
< / span > < span class = "comment" > //
< / 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" > range_mutable_iterator< / span > < span class = "special" > < < / span > < span class = "identifier" > Foo< / span > < span class = "special" > ::< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > T< / span > < span class = "special" > > < / span > < span class = "special" > > < / span >
< span class = "special" > {< / span >
< span class = "keyword" > typedef< / span > < span class = "identifier" > T< / span > < span class = "identifier" > type< / 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" > range_const_iterator< / span > < span class = "special" > < < / span > < span class = "identifier" > Foo< / span > < span class = "special" > ::< / span > < span class = "identifier" > Pair< / 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" > //
< / span > < span class = "comment" > // Remark: this is defined similar to 'range_iterator'
< / span > < span class = "comment" > // because the 'Pair' type does not distinguish
< / span > < span class = "comment" > // between an iterator and a const_iterator.
< / span > < span class = "comment" > //
< / span > < span class = "keyword" > typedef< / span > < span class = "identifier" > T< / span > < span class = "identifier" > type< / span > < span class = "special" > ;< / span >
< span class = "special" > };< / span >
< span class = "special" > }< / span > < span class = "comment" > // namespace 'boost'
< / span >
< span class = "keyword" > namespace< / span > < span class = "identifier" > Foo< / span >
< span class = "special" > {< / span >
< span class = "comment" > //
< / span > < span class = "comment" > // The required functions. These should be defined in
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< / span > < span class = "comment" > // the same namespace as 'Pair', in this case
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< / span > < span class = "comment" > // in namespace 'Foo'.
< / span > < span class = "comment" > //
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< / span >
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< 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" > inline< / span > < span class = "identifier" > T< / span > < span class = "identifier" > range_begin< / span > < span class = "special" > (< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > T< / span > < span class = "special" > > & < / span > < span class = "identifier" > x< / span > < span class = "special" > )< / span >
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< span class = "special" > {< / span >
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< span class = "keyword" > return< / span > < span class = "identifier" > x< / span > < span class = "special" > .< / span > < span class = "identifier" > first< / 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" > inline< / span > < span class = "identifier" > T< / span > < span class = "identifier" > range_begin< / span > < span class = "special" > (< / span > < span class = "keyword" > const< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > T< / span > < span class = "special" > > & < / span > < span class = "identifier" > x< / span > < span class = "special" > )< / span >
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< span class = "special" > {< / span >
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< span class = "keyword" > return< / span > < span class = "identifier" > x< / span > < span class = "special" > .< / span > < span class = "identifier" > first< / 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" > inline< / span > < span class = "identifier" > T< / span > < span class = "identifier" > range_end< / span > < span class = "special" > (< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > T< / span > < span class = "special" > > & < / span > < span class = "identifier" > x< / span > < span class = "special" > )< / span >
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< span class = "special" > {< / span >
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< span class = "keyword" > return< / span > < span class = "identifier" > x< / span > < span class = "special" > .< / span > < span class = "identifier" > last< / 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" > inline< / span > < span class = "identifier" > T< / span > < span class = "identifier" > range_end< / span > < span class = "special" > (< / span > < span class = "keyword" > const< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > T< / span > < span class = "special" > > & < / span > < span class = "identifier" > x< / span > < span class = "special" > )< / span >
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< span class = "special" > {< / span >
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< span class = "keyword" > return< / span > < span class = "identifier" > x< / span > < span class = "special" > .< / span > < span class = "identifier" > last< / span > < span class = "special" > ;< / span >
< span class = "special" > }< / span >
< span class = "special" > }< / span > < span class = "comment" > // namespace 'Foo'
< / span >
< span class = "preprocessor" > #include< / span > < span class = "special" > < < / span > < span class = "identifier" > vector< / span > < span class = "special" > > < / span >
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< span class = "keyword" > int< / span > < span class = "identifier" > main< / span > < span class = "special" > (< / span > < span class = "keyword" > int< / span > < span class = "identifier" > argc< / span > < span class = "special" > ,< / span > < span class = "keyword" > const< / span > < span class = "keyword" > char< / span > < span class = "special" > *< / span > < span class = "identifier" > argv< / span > < span class = "special" > [])< / span >
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< span class = "special" > {< / span >
< span class = "keyword" > typedef< / span > < span class = "identifier" > std< / 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" > iterator< / span > < span class = "identifier" > iter< / 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 = "keyword" > int< / span > < span class = "special" > > < / span > < span class = "identifier" > vec< / span > < span class = "special" > ;< / span >
< span class = "identifier" > Foo< / span > < span class = "special" > ::< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > iter< / span > < span class = "special" > > < / span > < span class = "identifier" > pair< / span > < span class = "special" > =< / span > < span class = "special" > {< / span > < span class = "identifier" > vec< / span > < span class = "special" > .< / span > < span class = "identifier" > begin< / span > < span class = "special" > (),< / span > < span class = "identifier" > vec< / span > < span class = "special" > .< / span > < span class = "identifier" > end< / span > < span class = "special" > ()< / span > < span class = "special" > };< / span >
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< span class = "keyword" > const< / span > < span class = "identifier" > Foo< / span > < span class = "special" > ::< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > iter< / span > < span class = "special" > > & < / span > < span class = "identifier" > cpair< / span > < span class = "special" > =< / span > < span class = "identifier" > pair< / span > < span class = "special" > ;< / span >
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< span class = "comment" > //
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< / span > < span class = "comment" > // Notice that we call 'begin' etc with qualification.
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< / span > < span class = "comment" > //
< / span > < span class = "identifier" > iter< / span > < span class = "identifier" > i< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > begin< / span > < span class = "special" > (< / span > < span class = "identifier" > pair< / span > < span class = "special" > );< / span >
< span class = "identifier" > iter< / span > < span class = "identifier" > e< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > end< / span > < span class = "special" > (< / span > < span class = "identifier" > pair< / span > < span class = "special" > );< / span >
< span class = "identifier" > i< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > begin< / span > < span class = "special" > (< / span > < span class = "identifier" > cpair< / span > < span class = "special" > );< / span >
< span class = "identifier" > e< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > end< / span > < span class = "special" > (< / span > < span class = "identifier" > cpair< / span > < span class = "special" > );< / span >
< span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > range_difference< / span > < span class = "special" > < < / span > < span class = "identifier" > Foo< / span > < span class = "special" > ::< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > iter< / span > < span class = "special" > > < / span > < span class = "special" > > ::< / span > < span class = "identifier" > type< / span > < span class = "identifier" > s< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > size< / span > < span class = "special" > (< / span > < span class = "identifier" > pair< / span > < span class = "special" > );< / span >
< span class = "identifier" > s< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > size< / span > < span class = "special" > (< / span > < span class = "identifier" > cpair< / span > < span class = "special" > );< / span >
< span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > range_reverse_iterator< / span > < span class = "special" > < < / span > < span class = "keyword" > const< / span > < span class = "identifier" > Foo< / span > < span class = "special" > ::< / span > < span class = "identifier" > Pair< / span > < span class = "special" > < < / span > < span class = "identifier" > iter< / span > < span class = "special" > > < / span > < span class = "special" > > ::< / span > < span class = "identifier" > type< / span >
< span class = "identifier" > ri< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > rbegin< / span > < span class = "special" > (< / span > < span class = "identifier" > cpair< / span > < span class = "special" > ),< / span >
< span class = "identifier" > re< / span > < span class = "special" > =< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > rend< / span > < span class = "special" > (< / span > < span class = "identifier" > cpair< / span > < span class = "special" > );< / span >
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< span class = "keyword" > return< / span > < span class = "number" > 0< / span > < span class = "special" > ;< / span >
< span class = "special" > }< / span >
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< / pre >
< p >
< / p >
< / div >
< table xmlns:rev = "http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width = "100%" > < tr >
< td align = "left" > < / td >
< 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 > )
< / p >
< / div > < / td >
< / tr > < / table >
< hr >
< div class = "spirit-nav" >
< a accesskey = "p" href = "method_1.html" > < img src = "../../../../../../../doc/html/images/prev.png" alt = "Prev" > < / a > < a accesskey = "u" href = "../extending.html" > < img src = "../../../../../../../doc/html/images/up.png" alt = "Up" > < / a > < a accesskey = "h" href = "../../../index.html" > < img src = "../../../../../../../doc/html/images/home.png" alt = "Home" > < / a > < a accesskey = "n" href = "method_3.html" > < img src = "../../../../../../../doc/html/images/next.png" alt = "Next" > < / a >
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