Fixing opEquals and opCmp

[Fool via Digitalmars-d]

On Saturday, 13 May 2017 at 14:17:24 UTC, H. S. Teoh wrote:
>> Another misunderstanding. Currently, there is no means to 
>> express that 'less' models a partial order vs. a linear order.
>
> Wrong.  Andrei specifically stated before that opCmp may model 
> a partial order, i.e., returning 0 may indicate "not 
> comparable" rather than "equal".  And this is why opEquals is 
> necessary: to distinguish between "not comparable" and "equal".

How is this reflected in the interface?