Conversion to prove whether one rational literal of type :real is <=
The call REAL_RAT_LE_CONV `c1 <= c2` where c1 and c2 are rational
literals of type :real, returns whichever of |- c1 <= c2 <=> T or
|- c1 <= c2 <=> F is true. The literals c1 and c2 may be integer
literals (&n or -- &n), ratios (&p / &q or -- &p / &q), or decimals
(#DDD.DDDD or #DDD.DDDDeNN).
Fails if applied to a term that is not the appropriate inequality comparison on
two permitted rational literals of type :real.
# REAL_RAT_LE_CONV `#3.1415926 <= &22 / &7`;;
val it : thm = |- #3.1415926 <= &22 / &7 <=> T