Applies a conversion to the operator of an application.
DESCRIPTION
If c is a conversion that maps a term `t1` to the theorem |- t1 = t1',
then the conversion RATOR_CONV c maps applications of the form `t1 t2` to
theorems of the form:
|- (t1 t2) = (t1' t2)
That is, RATOR_CONV c `t1 t2` applies c to the operator of the
application `t1 t2`.
FAILURE CONDITIONS
RATOR_CONV c tm fails if tm is not an application or if tm has the form
`t1 t2` but the conversion c fails when applied to the term t1. The
function returned by RATOR_CONV c may also fail if the ML function
c:term->thm is not, in fact, a conversion (i.e. a function that maps a term
t to a theorem |- t = t').
EXAMPLE
# RATOR_CONV BETA_CONV `(\x y. x + y) 1 2`;;
val it : thm = |- (\x y. x + y) 1 2 = (\y. 1 + y) 2