std::projected
Defined in header <iterator> |
||
|---|---|---|
template< std::indirectly_readable I,
std::indirectly_regular_unary_invocable<I> Proj >
struct projected {
using value_type = std::remove_cvref_t<std::indirect_result_t<Proj&, I>>;
std::indirect_result_t<Proj&, I> operator*() const; // not defined
}; |
(1) | (since C++20) |
template< std::weakly_incrementable I, class Proj >
struct incrementable_traits<std::projected<I, Proj>> {
using difference_type = std::iter_difference_t<I>;
}; |
(2) | (since C++20) |
1) Class template
projected combines an
indirectly_readable type
I and a callable object type
Proj into a new
indirectly_readable type whose reference type is the result of applying
Proj to the
std::iter_reference_t<I>.
2) This specialization of
std::incrementable_traits makes
std::projected<I, Proj> a
weakly_incrementable type when
I is also a
weakly_incrementable type.
projected is used only to constrain algorithms that accept callable objects and projections, and hence its operator*() is not defined.
Template parameters
| I | - | an indirectly readable type |
| Proj | - | projection applied to a dereferenced I |
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