Subgoal *1/2
(IMPLIES (AND (NOT (ENDP A))
(EQUAL (APP (APP (CDR A) B) C)
(APP (CDR A) (APP B C))))
(EQUAL (APP (APP A B) C)
(APP A (APP B C)))).
By the simple :definition ENDP we reduce the conjecture to
Subgoal *1/2'
(IMPLIES (AND (CONSP A)
(EQUAL (APP (APP (CDR A) B) C)
(APP (CDR A) (APP B C))))
(EQUAL (APP (APP A B) C)
(APP A (APP B C)))).
But simplification reduces this to T, using the :definition APP, the
:rewrite rules CDR-CONS and CAR-CONS and primitive type reasoning.