[indirectcallable] (original) (raw)

24 Iterators library [iterators]

24.3 Iterator requirements [iterator.requirements]

24.3.6 Indirect callable requirements [indirectcallable]

24.3.6.1 General [indirectcallable.general]

24.3.6.2 Indirect callable traits [indirectcallable.traits]

24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]

24.3.6.4 Alias template projected [projected]

24.3.6.1 General [indirectcallable.general]

There are several concepts that group requirements of algorithms that take callable objects ([func.def]) as arguments.

24.3.6.2 Indirect callable traits [indirectcallable.traits]

To implement algorithms taking projections, it is necessary to determine the projected type of an iterator's value type.

For the exposition-only alias template indirect-value-t,indirect-value-t<T> denotes

24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]

The indirect callable concepts are used to constrain those algorithms that accept callable objects ([func.def]) as arguments.

namespace std { template<class F, class I> concept indirectly_unary_invocable = indirectly_readable<I> && copy_constructible<F> && invocable<F&, _indirect-value-t_<I>> && invocable<F&, iter_reference_t<I>> && common_reference_with< invoke_result_t<F&, _indirect-value-t_<I>>, invoke_result_t<F&, iter_reference_t<I>>>;template<class F, class I> concept indirectly_regular_unary_invocable = indirectly_readable<I> && copy_constructible<F> && regular_invocable<F&, _indirect-value-t_<I>> && regular_invocable<F&, iter_reference_t<I>> && common_reference_with< invoke_result_t<F&, _indirect-value-t_<I>>, invoke_result_t<F&, iter_reference_t<I>>>;template<class F, class I> concept indirect_unary_predicate = indirectly_readable<I> && copy_constructible<F> && predicate<F&, _indirect-value-t_<I>> && predicate<F&, iter_reference_t<I>>;template<class F, class I1, class I2> concept indirect_binary_predicate = indirectly_readable<I1> && indirectly_readable<I2> && copy_constructible<F> && predicate<F&, _indirect-value-t_<I1>, indirect-value-t<I2>> && predicate<F&, _indirect-value-t_<I1>, iter_reference_t<I2>> && predicate<F&, iter_reference_t<I1>, indirect-value-t<I2>> && predicate<F&, iter_reference_t<I1>, iter_reference_t<I2>>;template<class F, class I1, class I2 = I1> concept indirect_equivalence_relation = indirectly_readable<I1> && indirectly_readable<I2> && copy_constructible<F> && equivalence_relation<F&, _indirect-value-t_<I1>, indirect-value-t<I2>> && equivalence_relation<F&, _indirect-value-t_<I1>, iter_reference_t<I2>> && equivalence_relation<F&, iter_reference_t<I1>, indirect-value-t<I2>> && equivalence_relation<F&, iter_reference_t<I1>, iter_reference_t<I2>>;template<class F, class I1, class I2 = I1> concept indirect_strict_weak_order = indirectly_readable<I1> && indirectly_readable<I2> && copy_constructible<F> && strict_weak_order<F&, _indirect-value-t_<I1>, indirect-value-t<I2>> && strict_weak_order<F&, _indirect-value-t_<I1>, iter_reference_t<I2>> && strict_weak_order<F&, iter_reference_t<I1>, indirect-value-t<I2>> && strict_weak_order<F&, iter_reference_t<I1>, iter_reference_t<I2>>;}

24.3.6.4 Alias template projected [projected]

Alias template projected is used to constrain algorithms that accept callable objects and projections ([defns.projection]).

It 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 applyingProj to the iter_reference_t of I.

namespace std { template<class I, class Proj> struct projected-impl { struct type { using value_type = remove_cvref_t<indirect_result_t<Proj&, I>>;using difference_type = iter_difference_t<I>; indirect_result_t<Proj&, I> operator*() const; };};template<indirectly_readable I, indirectly_regular_unary_invocable<I> Proj> using projected = projected-impl<I, Proj>::type;}