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std::indirect_equivalence_relation

From cppreference.com
< cpp‎ | iterator
 
 
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
indirect_equivalence_relation
(C++20)
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)

Iterator adaptors
Iterator customization points
Iterator operations
(C++11)    
(C++11)
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(C++11)(C++14)
(C++14)(C++14)    
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(C++14)(C++14)    
(C++17)(C++20)
(C++17)
(C++17)
 
Defined in header <iterator>
template< class F, class I1, class I2 = I1 >

concept indirect_equivalence_relation =
    std::indirectly_readable<I1> &&
    std::indirectly_readable<I2> &&
    std::copy_constructible<F> &&
    std::equivalence_relation<F&, std::iter_value_t<I1>&, std::iter_value_t<I2>&> &&
    std::equivalence_relation<F&, std::iter_value_t<I1>&, std::iter_reference_t<I2>> &&
    std::equivalence_relation<F&, std::iter_reference_t<I1>, std::iter_value_t<I2>&> &&
    std::equivalence_relation<F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>> &&
    std::equivalence_relation<F&, std::iter_common_reference_t<I1>,

                                  std::iter_common_reference_t<I2>>;
(since C++20)

The concept indirect_equivalence_relation specifies requirements for algorithms that call equivalence relations as their arguments. The key difference between this concept and std::equivalence_relation is that it is applied to the types that I1 and I2 references, rather than I1 and I2 themselves.

[edit] Semantic requirements

F, I1, and I2 model indirect_equivalence_relation only if all concepts it subsumes are modeled.