std::indirect_strict_weak_order
        <iterator> 
 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 
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.
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_orderrequired F& to satisfystrict_weak_orderwith std::iter_common_reference_t <I> | does not require |