Simplify a term once by conditional contextual rewriting.
DESCRIPTION
A call ONCE_SIMP_CONV thl tm will return |- tm = tm' where tm' results
from applying the theorems in thl as (conditional) rewrite rules, as well as
built-in simplifications (see basic_rewrites and basic_convs). For more
details on this kind of conditional rewriting, see SIMP_TAC. The ONCE
prefix indicates that the first applicable terms in a toplevel term will be
simplified once only, though conditional subgoals generated will be simplified
repeatedly.
FAILURE CONDITIONS
Never fails, but may return a reflexive theorem |- tm = tm if no
simplifications can be made.