On 9/28/2016 2:48 AM, Matthias Bentrup wrote:
In Mathematics the comparison operators are also commonly used for semi orders,
which cannot be implemented by opCmp, because opCmp has no way to indicate that
two values are incomparable.
Interestingly the floating point types are semi ordered (due to NaNs), and for
those D has some (non-overridable and deprecated) operators like !<, which would
be easily extendable to any semi order, whereas the suggested replacement (i.e.
test for NaNs manually) works only on floats.
I'm aware of the limitation, and a fair amount of thought was given on it, but
the solution used generally for unordered is to test for it separately, and
people seem happy with it.
The !<, etc., operators have been an utter failure (not a failure technically,
but people found them hopelessly confusing and would not use them).
