24 Algorithms library [algorithms]

24.7 Sorting and related operations [alg.sorting]

24.7.3 Binary search [alg.binary.search]

24.7.3.4 binary_­search [binary.search]

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); namespace ranges { template<ForwardIterator I, Sentinel<I> S, class T, class Proj = identity, IndirectStrictWeakOrder<const T*, projected<I, Proj>> Comp = ranges::less<>> constexpr bool binary_search(I first, S last, const T& value, Comp comp = {}, Proj proj = {}); template<ForwardRange R, class T, class Proj = identity, IndirectStrictWeakOrder<const T*, projected<iterator_t<R>, Proj>> Comp = ranges::less<>> constexpr bool binary_search(R&& r, const T& value, Comp comp = {}, Proj proj = {}); }
Let comp be less{} and proj be identity{} for overloads with no parameters by those names.
Requires: The elements e of [first, last) shall be 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)) shall imply !bool(comp(​value, e)) for the overloads in namespace std.
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.
Complexity: At most comparisons and projections.