Is there any interest in fixing opEquals and opCmp in the
spirit(*) of [1]?
Translating the basic idea into the D world would mean:
- Drop opEquals
- Encode the type of comparison in the return type of opCmp
- Adapt lowering
Why?
- Simplicity: there is always only one function that needs to be
implemented;
- Consistency: implementation at a single place makes it more
difficult to get it wrong;
- Expressivity: through the return type implementors can
unambiguously specify the properties of comparison relations
(Equivalence, Equality, PartialOrdering, LinearOrdering, etc.)
and algorithms can more precisely specify their requirements
(e.g. general sorting requires a weak ordering whereas
topological sorting requires a preorder, only);
[1] Herb Sutter: Consistent comparison, P0515 R0, 2017-02-05
URL
http://open-std.org/JTC1/SC22/WG21/docs/papers/2017/p0515r0.pdf
(*) Some aspects of the proposal are unsound but those can be
easily fixed.
