std::indirectly_unary_invocable, std::indirectly_regular_unary_invocable

 

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indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_output_iterator (C++20)	forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
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input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (deprecated in C++17) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
Algorithm concepts and utilities
Indirect callable concepts
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)	indirect_unary_predicate (C++20) indirect_binary_predicate (C++20)	indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20)	indirectly_copyable_storable (C++20)   indirectly_swappable (C++20) indirectly_comparable (C++20)	permutable (C++20) mergeable (C++20) sortable (C++20)
Utilities
indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
Iterator adaptors
reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter move_sentinel (C++20)	common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) make_const_iterator (C++23) make_const_sentinel (C++23)
Stream iterators istream_iterator    ostream_iterator istreambuf_iterator ostreambuf_iterator	Iterator customization points ranges::iter_move (C++20) ranges::iter_swap (C++20)
Iterator operations advance distance prev (C++11)   next (C++11) ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)	Range access begincbegin (C++11)(C++14) rbegincrbegin (C++14)(C++14)   endcend (C++11)(C++14) rendcrend (C++14)(C++14)   sizessize (C++17)(C++20) empty (C++17) data (C++17)

 

Defined in header <iterator>
std::indirectly_unary_invocable
template< class F, class I >     concept indirectly_unary_invocable =         std::indirectly_readable<I> &&         std::copy_constructible<F> &&         std::invocable<F&, std::iter_value_t<I>&> &&         std::invocable<F&, std::iter_reference_t<I>> &&         std::invocable<F&, std::iter_common_reference_t<I>> &&         std::common_reference_with<             std::invoke_result_t<F&, std::iter_value_t<I>&>,             std::invoke_result_t<F&, std::iter_reference_t<I>>>;		(since C++20) (until C++26)
template< class F, class I >     concept indirectly_unary_invocable =         std::indirectly_readable<I> &&         std::copy_constructible<F> &&         std::invocable<F&, std::iter_value_t<I>&> &&         std::invocable<F&, std::iter_reference_t<I>> &&         std::common_reference_with<             std::invoke_result_t<F&, std::iter_value_t<I>&>,             std::invoke_result_t<F&, std::iter_reference_t<I>>>;		(since C++26)
std::indirectly_regular_unary_invocable
template< class F, class I >     concept indirectly_regular_unary_invocable =         std::indirectly_readable<I> &&         std::copy_constructible<F> &&         std::regular_invocable<F&, std::iter_value_t<I>&> &&         std::regular_invocable<F&, std::iter_reference_t<I>> &&         std::regular_invocable<F&, std::iter_common_reference_t<I>> &&         std::common_reference_with<             std::invoke_result_t<F&, std::iter_value_t<I>&>,             std::invoke_result_t<F&, std::iter_reference_t<I>>>;		(since C++20) (until C++26)
template< class F, class I >     concept indirectly_regular_unary_invocable =         std::indirectly_readable<I> &&         std::copy_constructible<F> &&         std::regular_invocable<F&, std::iter_value_t<I>&> &&         std::regular_invocable<F&, std::iter_reference_t<I>> &&         std::common_reference_with<             std::invoke_result_t<F&, std::iter_value_t<I>&>,             std::invoke_result_t<F&, std::iter_reference_t<I>>>;		(since C++26)

The concepts indirectly_unary_invocable and indirectly_regular_unary_invocable specify requirements for algorithms that call (regular) unary invocables as their arguments. The key difference between these concepts and std::invocable is that they are applied to the type the I references, rather than I itself.

Notes

The distinction between indirectly_unary_invocable and indirectly_regular_unary_invocable is purely semantic.