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std::indirectly_unary_invocable, std::indirectly_regular_unary_invocable

Defined in header <iterator> 
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) 
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)

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.

Semantic requirements

Each concept is modeled by F and I only if all concepts it subsume are modeled.

Notes

The distinction between indirectly_unary_invocable and indirectly_regular_unary_invocable is purely semantic.

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