expression templates

[KennyTM~]

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;