WAT: opCmp and opEquals woes

[H. S. Teoh via Digitalmars-d]

On Wed, Jul 23, 2014 at 02:35:03PM -0700, Andrei Alexandrescu via Digitalmars-d wrote:
> On 7/23/14, 11:52 AM, H. S. Teoh via Digitalmars-d wrote:
[...]
> >I fully agree that we should not autogenerate opCmp if the user
> >defines opEquals, since not all types comparable with equality are
> >orderable.  However, surely all orderable types are
> >equality-comparable!
> 
> http://en.wikipedia.org/wiki/Lattice_(order)
[...]

And why should this be the default behaviour? The <, <=, >=, > operators
imply linear ordering, not general partial order. If you really want to
implement a non-linear partial ordering, you can always define both
opCmp and opEquals. This should be the *non*-default case, since in the
vast majority of cases, defining opCmp means you want a linear ordering.
Linear ordering should be default, and partial ordering possible if the
programmer explicitly asks for it (by implementing opEquals manually).


T

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