Create two lisp functions.

Create two lisp functions.

  (apply-sub expr sub)> (apply-sub '(p ?x (f ?y) b) '((?z ?x) (?w ?y)))  (p ?z (f ?w) b)> (apply-sub '(p ?x (f ?y) b) '(((g ?z) ?x) (bill ?y)))  (p (g ?z) (f bill) b)  (compose sub1 sub2)> (compose '((?x ?z) (?w ?y)) '((a ?x) (b ?v)))  ((a ?z) (?w ?y) (a ?x) (b ?v))> (compose '(((g ?x ?y) ?z)) '((a ?x) (b ?y) (c ?w) (d ?z)))  (((g a b) ?z) (a ?x) (b ?y) (c ?w))  (defun isvar (x)     (cond ((null x) nil)           ((pair x) nil)           (t (equal "?" (substring (symbol->string x) 0 1)))     )  )> (isvar '?x)#t> (isvar 'bill)#f