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3324. Special-casestd::strong/weak/partial_order for pointers

Section: 17.12.6[cmp.alg]Status:C++20Submitter: CanadaOpened: 2019-11-06Last modified: 2021-02-25

Priority:0

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Discussion:

AddressesCA 178

std::strong_order,weak_order, andpartial_order have special cases for floating point, but are missing special casing for pointers.compare_three_way andstd::less have the special casing for pointers.

Change [cmp.alg] bullet 1.4 from
"Otherwise,strong_ordering(E <=> F) if it is a well-formed expression."
to
"Otherwise,strong_ordering(compare_three_way()(E, F)) if it is a well-formed expression."

Change [cmp.alg] bullet 2.4 from
"Otherwise,weak_ordering(E <=> F) if it is a well-formed expression."
to
"Otherwise,weak_ordering(compare_three_way()(E, F)) if it is a well-formed expression."
Change [cmp.alg] bullet 3.3 from
"Otherwise,partial_ordering(E <=> F) if it is a well-formed expression."
to
"Otherwise,partial_ordering(compare_three_way()(E, F)) if it is a well-formed expression."

Dietmar Kühl:

Usecompare_three_way instead of<=> for the various comparison algorithms.

[2019-11 Status to Ready during Wednesday night issue processing in Belfast.]

Proposed resolution:

This wording is relative toN4835.

1. Change 17.12.6[cmp.alg] as indicated:

   -1- The namestrong_order […]

   1. […]

   2. (1.4) — Otherwise,strong_ordering(E <=> Fcompare_three_way()(E, F)) if it is a well-formed expression.

   3. […]

   -2- The nameweak_order […]

   1. […]

   2. (2.4) — Otherwise,weak_ordering(E <=> Fcompare_three_way()(E, F)) if it is a well-formed expression.

   3. […]

   -3- The namepartial_order […]

   1. […]

   2. (3.3) — Otherwise,partial_ordering(E <=> Fcompare_three_way()(E, F)) if it is a well-formed expression.

   3. […]