# std::indirect_unary_predicate

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< cpp‎ | iterator

Defined in header `<iterator>` |  |
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>>; |  | (since C++20)

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.

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