P1188 Library utilities for <=>

[jensmaurer]

P1188R0 Library utilities for <=> (Barry Revzin)

https://issues.isocpp.org/show_bug.cgi?id=525

[tituswinters]

LEWG in Kona:
Change the name from compare_3way_type_t to compare_3way_result_t.
SF F N A SA
7 7 1 0 0

Clean up all spellings of 3way to three_way / ThreeWay.
SF F N A SA
2 6 6 1 0

Do the above, come back with a revision that also replaces compare_3way with the comparison object that invokes <=> and introduces compare_three_way_fallback.
SF F N A SA
3 8 2 0 0

Threeway is one word.
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0 3 6 5 2

In light of not wanting the assume_ functions in P0891, we continue to want compare_three_way_fallback.
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1 3 5 1 1

We want a fallback/bridging mechanism, we want it to obey the strong_order customization point family, we tentatively like the ordering being provided via template parameter.
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1 12 0 0 0

(The fallback/bridging API probably goes into a revision of P0891).

[tituswinters]

Non-member, hidden friend, or member.

Make them hidden friends.
Unanimous consent

Extension form for partial-ordered strings.

char_traits specialization: member alias vs. static member function.
Prefer member alias.
SF F N A SA
2 5 4 0 1

General approval per design form (unique_ptr, optional, string, vector)-like.

Approve the design direction for smart pointers.
Unanimous consent

Approve the design direction for optional/variant/stack/queue/reverse_iterator (types that wrap an underlying but make no assumptions about the semantics of underlying comparison operators).
Unanimous consent

Approve the design direction for vector and other lexicographically-ordered types.
Unanimous consent

Approve the design direction for basic_string.
Unanimous consent

Approve the design direction for removal of operator!=, and operator==’s that are unnecessary because of P1185.
Unanimous consent

Add the explicit defaulting for the relevant types (pair, array) - NOT tuple.
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3 6 1 0 0

Forward to LWG for C++20.
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9 2 0 0 0

[tituswinters]

(There's a possible mix-up between numbers: I'm seeing this listed as both P1188 and P1189 in various places.)

[jensmaurer]

Integrated into P1614 The Mothership Has Landed: Adding <=> to the Library #391.