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inner_product avoids pre-condition check with input_iterators due to single-pass limitation.

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This commit is contained in:
Neil Groves
2014-02-27 13:51:06 +00:00
parent 259e917eaf
commit fd0f99c767
1 changed files with 36 additions and 2 deletions
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38
include/boost/range/numeric.hpp
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@ -30,8 +30,10 @@
#include <boost/assert.hpp>
#include <boost/range/begin.hpp>
#include <boost/range/end.hpp>
#include <boost/range/category.hpp>
#include <boost/range/concepts.hpp>
#include <boost/range/distance.hpp>
#include <boost/range/size.hpp>
#include <numeric>
@ -51,13 +53,41 @@ namespace boost
return std::accumulate( boost::begin(rng), boost::end(rng), init, op );
}
namespace range_detail
{
template<class SinglePassRange1, class SinglePassRange2>
inline bool inner_product_precondition(
const SinglePassRange1&,
const SinglePassRange2&,
std::input_iterator_tag,
std::input_iterator_tag)
{
return true;
}
template<class SinglePassRange1, class SinglePassRange2>
inline bool inner_product_precondition(
const SinglePassRange1& rng1,
const SinglePassRange2& rng2,
std::forward_iterator_tag,
std::forward_iterator_tag)
{
return boost::size(rng2) >= boost::size(rng1);
}
} // namespace range_detail
template< class SinglePassRange1, class SinglePassRange2, class Value >
inline Value inner_product( const SinglePassRange1& rng1, const SinglePassRange2& rng2, Value init )
{
BOOST_RANGE_CONCEPT_ASSERT(( SinglePassRangeConcept<const SinglePassRange1> ));
BOOST_RANGE_CONCEPT_ASSERT(( SinglePassRangeConcept<const SinglePassRange2> ));
BOOST_ASSERT( boost::distance(rng2) >= boost::distance(rng1) );
BOOST_ASSERT(
range_detail::inner_product_precondition(
rng1, rng2,
typename range_category<const SinglePassRange1>::type(),
typename range_category<const SinglePassRange2>::type()));
return std::inner_product( boost::begin(rng1), boost::end(rng1),
boost::begin(rng2), init );
}
@ -72,7 +102,11 @@ namespace boost
{
BOOST_RANGE_CONCEPT_ASSERT(( SinglePassRangeConcept<const SinglePassRange1> ));
BOOST_RANGE_CONCEPT_ASSERT(( SinglePassRangeConcept<const SinglePassRange2> ));
BOOST_ASSERT( boost::distance(rng2) >= boost::distance(rng1) );
BOOST_ASSERT(
range_detail::inner_product_precondition(
rng1, rng2,
typename range_category<const SinglePassRange1>::type(),
typename range_category<const SinglePassRange2>::type()));
return std::inner_product( boost::begin(rng1), boost::end(rng1),
boost::begin(rng2), init, op1, op2 );