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45 lines
1.5 KiB
ReStructuredText
45 lines
1.5 KiB
ReStructuredText
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.. _sprout-algorithm-count_if:
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###############################################################################
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count_if
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###############################################################################
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Interface
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========================================
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.. sourcecode:: c++
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template<typename InputIterator, typename Predicate>
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inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
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count_if(InputIterator first, InputIterator last, Predicate pred);
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Returns
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========================================
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| The number of iterators i in the range [first,last) for which the following corresponding conditions hold: ``pred(*i)``.
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Examples
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========================================
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.. sourcecode:: c++
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#include <sprout/algorithm/count_if.hpp>
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#include <sprout/array.hpp>
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#include <sprout/container.hpp>
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#include <sprout/functional.hpp>
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using namespace sprout;
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SPROUT_STATIC_CONSTEXPR auto input = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
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SPROUT_STATIC_CONSTEXPR auto result = sprout::count_if(begin(input), end(input), bind2nd(modulus<>(), 2));
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static_assert(result == 5, "counted 5 elements of odd number from input.");
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Complexity
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========================================
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| Exactly ``last - first`` applications of the predicate.
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| Recursive function invocations in *O(logN)* (logarithmic) depth.
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Header
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========================================
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| ``sprout/algorithm/count_if.hpp``
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| Convenience header: ``sprout/algorithm.hpp``
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