rand
Term.rand : term -> term
Returns the operand from a combination (function application).
If M is a combination, i.e., has the form (t1 t2), then rand M returns t2.
M
(t1 t2)
rand M
t2
Fails if M is not a combination.
Term.rator, Term.dest_comb
Term.rator
Term.dest_comb