std::indirect_unary_predicate

template<class F, class I>
concept indirect_unary_predicate =
  std::indirectly_readable<I> &&
  std::copy_constructible<F> &&
  std::predicate<F&, std::iter_value_t<I>&> &&
  std::predicate<F&, std::iter_reference_t<I>> &&
  std::predicate<F&, std::iter_common_reference_t<I>>;

The concept indirect_unary_predicate specifies requirements for algorithms that call unary predicates as their arguments. The key difference between this concept and std::predicate is that it is applied to the type that I references, rather than I itself.

Semantic requirements

F and I model indirect_unary_predicate only if all concepts it subsumes are modeled.