WAT: opCmp and opEquals woes

[Walter Bright via Digitalmars-d]

On 7/24/2014 10:52 PM, Manu via Digitalmars-d wrote:
> I don't really see how opCmp == 0 could be unreliable or unintended. It was
> deliberately written by the author, so definitely not unintended, and I can't
> imagine anybody would ever deliberately ignore the == 0 case when implementing
> an opCmp, or produce logic that works for less or greater, but fails for equal.
> <= and >= are expressed by opCmp, which imply that testing for equality
> definitely works as the user intended.

Yes, that's why it's hard to see that it would break existing code, unless that 
existing code had a bug in it that was worked around in some peculiar way.


> In lieu of an opEquals, how can a deliberately implemented opCmp, which we know
> works in the == case (otherwise <= or >= wouldn't work either) ever be a worse
> choice than an implicitly generated opEquals?

Determining an ordering can sometimes be more expensive. It is, after all, 
asking for more information.