----------------------------------------------------------------------
rator                                                           (Term)
----------------------------------------------------------------------
rator : term -> term

SYNOPSIS
Returns the operator from a combination (function application).

DESCRIBE
If {M} is a combination, i.e., has the form {(t1 t2)}, then
{rator M} returns {t1}.

FAILURE
Fails if {M} is not a combination.

SEEALSO
Term.rand, Term.dest_comb.

----------------------------------------------------------------------