25 Iterators library [iterators]

25.3 Iterator requirements [iterator.requirements]

25.3.6 Indirect callable requirements [indirectcallable]

25.3.6.3 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>> && invocable<F&, iter_common_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>> && regular_invocable<F&, iter_common_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>> && predicate<F&, iter_common_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>> && predicate<F&, iter_common_reference_t<I1>, iter_common_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>> && equivalence_relation<F&, iter_common_reference_t<I1>, iter_common_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>> && strict_weak_order<F&, iter_common_reference_t<I1>, iter_common_reference_t<I2>>; }