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P0768R1 Library Support For The Spaceship Comparison Operator <=> #64

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StephanTLavavej opened this issue Sep 6, 2019 · 6 comments · Fixed by #1370
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P0768R1 Library Support For The Spaceship Comparison Operator <=> #64

StephanTLavavej opened this issue Sep 6, 2019 · 6 comments · Fixed by #1370
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cxx20 C++20 feature fixed Something works now, yay!
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@StephanTLavavej
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StephanTLavavej commented Sep 6, 2019 •
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P0768R1 Library Support For The Spaceship Comparison Operator <=>
P1959R0 Removing weak_equality And strong_equality

This was partially implemented in VS 2019 16.0, but some work remains to be done.

This deprecates rel_ops.

Feature-test macro added by WG21-P1353 "Missing Feature Test Macros" (note that this value will be increased by #62 WG21-P1614 "Adding Spaceship <=> To The Library"):
#define __cpp_lib_three_way_comparison 201711L
@StephanTLavavej StephanTLavavej added the cxx20 C++20 feature label Sep 6, 2019
@CaseyCarter
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CaseyCarter commented Oct 29, 2019 •
edited by StephanTLavavej
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Remaining work: (Note that components of P0768R1 superseded by P1614R2 are not included here)

  • Implement lexicographical_compare_three_way in <algorithm>
  • Don't implement compare_3way, strong_equal, and weak_equal - they are removed by later proposals
  • Implement the [cmp.alg] CPOs from P1614R2:
    • strong_order
    • weak_order
    • partial_order
    • compare_strong_order_fallback
    • compare_weak_order_fallback
    • compare_partial_order_fallback
  • After completing the above, define __cpp_lib_three_way_comparison in yvals_core.h when _HAS_CXX20
  • Throughput tuning for common_comparison_category
  • Deprecate std::rel_ops
  • Implement P1959R0 Removing weak_equality And strong_equality

CaseyCarter added a commit to CaseyCarter/STL that referenced this issue Oct 31, 2019
@CaseyCarter
<compare> implement == for comparison categories
6163ea9 
WG21-P1614 "The Mothership has Landed" added `==` operators to the comparison category types (`weak_equality`, `strong_equality`, `partial_ordering`, `weak_ordering`, and `strong_ordering`) defined in `<compare>`. This PR implements those operators to bring the comparison category types up to spec once again. It also implements P1614R2's removal of operators that rewrite into calls to `operator==(X, nullptr_t)` for each comparison category type `X`.

Drive-by changes:
* Move the TODO list of tasks for WG21-P0768 "Library Support for the Spaceship (Comparison) Operator" completion out of `<compare>` and into microsoft#64
* Remove the `#if 0 // Not yet implemented` block from `<compare>`
@CaseyCarter CaseyCarter mentioned this issue Oct 31, 2019
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CaseyCarter added a commit that referenced this issue Nov 1, 2019
@CaseyCarter
<compare> implement == for comparison categories (#242)
1d09433 
WG21-P1614 "The Mothership has Landed" added `==` operators to the comparison category types (`weak_equality`, `strong_equality`, `partial_ordering`, `weak_ordering`, and `strong_ordering`) defined in `<compare>`. This PR implements those operators to bring the comparison category types up to spec once again. It also implements P1614R2's removal of operators that rewrite into calls to `operator==(X, nullptr_t)` for each comparison category type `X`.

Drive-by changes:
* Move the TODO list of tasks for WG21-P0768 "Library Support for the Spaceship (Comparison) Operator" completion out of `<compare>` and into #64
* Remove the `#if 0 // Not yet implemented` block from `<compare>`
@StephanTLavavej StephanTLavavej mentioned this issue Dec 4, 2019
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This was referenced Dec 11, 2019
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StephanTLavavej pushed a commit that referenced this issue Dec 13, 2019
@AdamBucior @StephanTLavavej
Remove weak_equality and strong_equality (#381)
07e85d1 
Implement WG21-P1959 Removing `weak_equality` And `strong_equality`, working towards #64.
@SuperWig SuperWig mentioned this issue Dec 21, 2019
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@AdamBucior
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I have lexicographical_compare_three_way implementation ready but I wait with it for #385 to be merged because it requires compare_three_way.

@AdamBucior AdamBucior mentioned this issue Feb 19, 2020
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StephanTLavavej pushed a commit that referenced this issue Mar 8, 2020
@AdamBucior
<xutility> lexicographical_compare_three_way (#515)
26b0629 
Works towards #64.
@StephanTLavavej
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@CaseyCarter, looking at your checklist above, is this paper complete except for the feature-test macro update?

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@CaseyCarter, looking at your checklist above, is this paper complete except for the feature-test macro update?

I struck features from the list that were removed or replaced by later proposals. That makes sense for removals, but for replacements we should implement the replacement feature before defining the feature-test macro. I've updated the list to mention both removals and replacements.

TLDR: We still need to define the (strong|partial|weak)_order customization point objects before defining the feature-test macro.

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Looking at the Changelog it seems that P1959R0 Removing weak_equality And strong_equality is missing. Not sure if it's intentional. (The PR that implemented it: #381)

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Looking at the Changelog it seems that P1959R0 Removing weak_equality And strong_equality is missing. Not sure if it's intentional. (The PR that implemented it: #381)

Good catch, @AdamBucior. This was simply an oversight. I've added a mention of P1959R0 to the 16.5 section of the Changelog. Thanks!

@StephanTLavavej StephanTLavavej self-assigned this Apr 29, 2020
@cbezault cbezault added this to the Conformance milestone May 7, 2020
@StephanTLavavej StephanTLavavej mentioned this issue Oct 14, 2020
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@StephanTLavavej StephanTLavavej added fixed Something works now, yay! and removed work in progress labels Oct 29, 2020
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Finish P0768R1 by adding Spaceship CPOs StephanTLavavej/STL
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@CaseyCarter @cbezault @StephanTLavavej @AdamBucior