cppdraft_translate/cppdraft/equal/range.md

[equal.range]

26 Algorithms library [algorithms]

26.8 Sorting and related operations [alg.sorting]

26.8.4 Binary search [alg.binary.search]

26.8.4.4 equal_range [equal.range]

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`template<class ForwardIterator, class T = iterator_traits::value_type> constexpr pair<ForwardIterator, ForwardIterator> equal_range(ForwardIterator first, ForwardIterator last, const T& value);

template<class ForwardIterator, class T = iterator_traits::value_type, class Compare> constexpr pair<ForwardIterator, ForwardIterator> equal_range(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);

template<forward_iterator I, sentinel_for S, class Proj = identity, class T = projected_value_t<I, Proj>, indirect_strict_weak_order<const T*, projected<I, Proj>> Comp = ranges::less> constexpr subrange ranges::equal_range(I first, S last, const T& value, Comp comp = {}, Proj proj = {}); template<forward_range R, class Proj = identity, class T = projected_value_t<iterator_t, Proj>, indirect_strict_weak_order<const T*, projected<iterator_t, Proj>> Comp = ranges::less> constexpr borrowed_subrange_t ranges::equal_range(R&& r, const T& value, Comp comp = {}, Proj proj = {}); `

1

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Let comp be less{} andproj be identity{} for overloads with no parameters by those names.

2

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Preconditions: The elements e of [first, last) are partitioned with respect to the expressionsbool(invoke(comp, invoke(proj, e), value)) and!bool(invoke(comp, value, invoke(proj, e))).

Also, for all elements e of [first, last),bool(comp(e, value)) implies !bool(comp(​value, e)) for the overloads in namespace std.

3

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Returns:

• (3.1)

For the overloads in namespace std:{lower_bound(first, last, value, comp), upper_bound(first, last, value, comp)}

• (3.2)

For the overloads in namespace ranges:{ranges::lower_bound(first, last, value, comp, proj), ranges::upper_bound(first, last, value, comp, proj)}

4

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Complexity: At most2∗log2(last - first)+O(1) comparisons and projections.