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Difference between revisions of "cpp/iterator/indirect strict weak order"

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< cpp‎ | iterator
(removes equality preservation since it's not a direct requirement for this concept)
(c -> c/core.)
 
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{{cpp/title|indirect_strict_weak_order}}
 
{{cpp/title|indirect_strict_weak_order}}
 
{{cpp/iterator/navbar}}
 
{{cpp/iterator/navbar}}
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{{dcl begin}}
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{{ddcl|header=iterator|since=c++20|1=
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{{dcl header | iterator}}
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template< class F, class I1, class I2 = I1 >
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{{dcl | since=c++20 | 1=
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−
template<class F, class I1, class I2 = I1>
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concept indirect_strict_weak_order =
 
concept indirect_strict_weak_order =
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  std::indirectly_readable<I1> &&
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    std::indirectly_readable<I1> &&
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  std::indirectly_readable<I2> &&
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    std::indirectly_readable<I2> &&
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  std::copy_constructible<F> &&
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    std::copy_constructible<F> &&
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  std::strict_weak_order<F&, std::iter_value_t<I1>&, std::iter_value_t<I2>&> &&
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    std::strict_weak_order
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  std::strict_weak_order<F&, std::iter_value_t<I1>&, std::iter_reference_t<I2>> &&
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        <F&, /*indirect-value-t*/<I1>, /*indirect-value-t*/<I2>> &&
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  std::strict_weak_order<F&, std::iter_reference_t<I1>, std::iter_value_t<I2>&> &&
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    std::strict_weak_order
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  std::strict_weak_order<F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>> &&
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        <F&, /*indirect-value-t*/<I1>, std::iter_reference_t<I2>> &&
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  std::strict_weak_order<F&, std::iter_common_reference_t<I1>, std::iter_common_reference_t<I2>>;
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    std::strict_weak_order
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        <F&, std::iter_reference_t<I1>, /*indirect-value-t*/<I2>> &&
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    std::strict_weak_order
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        <F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>>;
 
}}
 
}}
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{{dcl end}}
 
  
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The concept {{tt|indirect_strict_weak_order}} specifies requirements for algorithms that call strict weak orders as their arguments. The key difference between this concept and {{tt|std::strict_weak_order}} is that it is applied to the types that {{tt|I1}} and {{tt|I2}} references, rather than {{tt|I1}} and {{tt|I2}} themselves.
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The concept {{tt|indirect_strict_weak_order}} specifies requirements for algorithms that call strict weak orders as their arguments. The key difference between this concept and {{lc|std::strict_weak_order}} is that it is applied to the types that {{tt|I1}} and {{tt|I2}} references, rather than {{tt|I1}} and {{tt|I2}} themselves.
  
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===Semantic requirements===
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===Defect reports===
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{{tt|F}}, {{tt|I1}}, and {{tt|I2}} model {{tt|indirect_strict_weak_order}} only if all concepts it subsumes are modeled.
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{{dr list begin}}
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{{dr list item|paper=P2609R3|std=C++20|before=some requirements were defined in terms of<br>{{c/core|std::iter_value_t<I>&}} which mishandled projections<br>resulting in incompatibility with strict weak order {{c/core|F&}}|after=defined in terms of<br>{{c/core|/*indirect-value-t*/<I>}} to<br>correctly handle such projections}}
 +
{{dr list item|paper=P2997R1|std=C++20|before={{tt|indirect_strict_weak_order}} required {{c/core|F&}} to satisfy<br>{{lconcept|strict_weak_order}} with {{c/core|std::iter_common_reference_t<I>}}|after=does not require}}
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{{dr list end}}
  
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{{langlinks|es|ja|zh}}
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 17:01, 13 October 2024

 
C++
 
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
(C++20)
indirect_strict_weak_order
(C++20)
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Range access
(C++11)(C++14)
(C++14)(C++14)  
(C++11)(C++14)
(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_strict_weak_order =
    std::indirectly_readable<I1> &&
    std::indirectly_readable<I2> &&
    std::copy_constructible<F> &&
    std::strict_weak_order
        <F&, /*indirect-value-t*/<I1>, /*indirect-value-t*/<I2>> &&
    std::strict_weak_order
        <F&, /*indirect-value-t*/<I1>, std::iter_reference_t<I2>> &&
    std::strict_weak_order
        <F&, std::iter_reference_t<I1>, /*indirect-value-t*/<I2>> &&
    std::strict_weak_order

        <F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>>;
 (since C++20)

The concept indirect_strict_weak_order specifies requirements for algorithms that call strict weak orders as their arguments. The key difference between this concept and std::strict_weak_order is that it is applied to the types that I1 and I2 references, rather than I1 and I2 themselves.

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
P2609R3 C++20 some requirements were defined in terms of
std::iter_value_t<I>& which mishandled projections
resulting in incompatibility with strict weak order F& 		defined in terms of
/*indirect-value-t*/<I> to
correctly handle such projections
P2997R1 C++20 indirect_strict_weak_order required F& to satisfy
strict_weak_order with std::iter_common_reference_t<I> 		does not require
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