25 Algorithms library [algorithms]

25.8 Sorting and related operations [alg.sorting]

25.8.3 Binary search [alg.binary.search]

25.8.3.4 binary_­search [binary.search]

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template<class ForwardIterator, class T> constexpr bool binary_search(ForwardIterator first, ForwardIterator last, const T& value); template<class ForwardIterator, class T, class Compare> constexpr bool binary_search(ForwardIterator first, ForwardIterator last, const T& value, Compare comp); template<forward_­iterator I, sentinel_­for<I> S, class T, class Proj = identity, indirect_­strict_­weak_­order<const T*, projected<I, Proj>> Comp = ranges::less> constexpr bool ranges::binary_search(I first, S last, const T& value, Comp comp = {}, Proj proj = {}); template<forward_­range R, class T, class Proj = identity, indirect_­strict_­weak_­order<const T*, projected<iterator_t<R>, Proj>> Comp = ranges::less> constexpr bool ranges::binary_search(R&& r, const T& value, Comp comp = {}, Proj proj = {});
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Let comp be less{} and proj be identity{} for overloads with no parameters by those names.
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Preconditions: The elements e of [first, last) are partitioned with respect to the expressions bool(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.
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Returns: true if and only if for some iterator i in the range [first, last), !bool(invoke(comp, invoke(proj, *i), value)) && !bool(invoke(comp, value, invoke(proj, *i))) is true.
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Complexity: At most comparisons and projections.