expression templates

[dsimcha]

== Quote from KennyTM~ (kennytm at gmail.com)'s article
> On Mar 30, 11 03:15, dsimcha wrote:
> > == Quote from bearophile (bearophileHUGS at lycos.com)'s article
> >> The operator overloading done with opCmp is too much coarse even if you want to
> > implement sets with operators like<=<  >  >= == for subset, etc.
> >
> > Can you please give an example of where<=,>, etc. are useful for representing
> > set operations?  My naive opinion (i.e. without understanding your use case) is
> > that using comparison operators to represent anything besides partial or total
> > ordering is a severe abuse of operator overloading.  (Their use to represent
> > ordering of corresponding elements of a vector or matrix is a borderline case.)
> If 'a <= b' means 'a' is a subset of 'b', then (Set, <=) does form a
> partial order.
> That said, the current opCmp design is capable of comparing sets and any
> partial orders if the return type can be relaxed to 'float':
>      if (a == b) return 0;
>      else if (a is subset of b) return -1;
>      else if (b is subset of a) return 1;
>      else /* unordered */ return NaN;

Technically you're right, but I question whether thinking of this as an ordering
is ever useful in practice.