std::indirectly_readable
    <iterator> 
     concept __IndirectlyReadableImpl =
        requires(const In in) {
            typename std::iter_value_t <In>;
            typename std::iter_reference_t <In>;
            typename std::iter_rvalue_reference_t <In>;
            { *in } -> std::same_as <std::iter_reference_t <In>>;
            { ranges::iter_move (in) } -> std::same_as <std::iter_rvalue_reference_t <In>>;
        } &&
        std::common_reference_with <
            std::iter_reference_t <In>&&, std::iter_value_t <In>&
        > &&
        std::common_reference_with <
            std::iter_reference_t <In>&&, std::iter_rvalue_reference_t <In>&&
        > &&
        std::common_reference_with <
            std::iter_rvalue_reference_t <In>&&, const std::iter_value_t <In>&
    concept indirectly_readable =
The concept indirectly_readable is modeled by types that are readable by applying operator*, such as pointers, smart pointers, and input iterators.
[edit] Semantic requirements
Given a value i of type I, I models indirectly_readable only if all concepts it subsumes are modeled and the expression *i is equality-preserving.
[edit] Equality preservation
Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise).