Integral types that define opCmp, opEquals

[Frits van Bommel]

Henning Hasemann wrote:
>> IIRC 'is' tests if a _type_ is valid. Try something like is(typeof(i < i)).
> 
> Works quite well, only thing is that
> it yields true for everything that is derived from object,
> but these indeed *have* defined opCmp so I guess
> there is no real way to find out if the writer of
> a class things this class' objects should be comparable
> to themselves.

No, AFAIK there indeed isn't, but there *is* a way to see if a class has 
an overridden Object.opCmp: (warning: dirty trick)
---
import std.stdio;

class Foo {	// opCmp overridden
	int opCmp(Object o) { return 0; }
}

class Bar { }	// opCmp not overridden

void main()
{
	writefln(&Foo.opCmp != &Object.opCmp);	// prints "true"
	writefln(&Bar.opCmp != &Object.opCmp);	// prints "false"
}
---