Applies a conversion to the two sides of an application.
If c is a conversion such that c `f` returns |- f = f' and
c `x` returns |- x = x', then COMB_CONV c `f x` returns
|- f x = f' x'. That is, the conversion c is applied to the two
- FAILURE CONDITIONS
Never fails when applied to the initial conversion. On application to the term,
it fails if conversion given as the argument does, or if the theorem returned
by it is inappropriate.
- SEE ALSO
BINOP_CONV, COMB2_CONV, LAND_CONV, RAND_CONV, RATOR_CONV