Exercise 5.31: In evaluating a procedure
application, the explicit-control evaluator always saves and restores the
env register around the evaluation of the operator, saves and restores
env around the evaluation of each operand (except the final one), saves
and restores argl around the evaluation of each operand, and saves and
restores proc around the evaluation of the operand sequence.  For each
of the following combinations, say which of these save and
restore operations are superfluous and thus could be eliminated by the
compiler’s preserving mechanism:


(f 'x 'y)
((f) 'x 'y)
(f (g 'x) y)
(f (g 'x) 'y)