<> (defer ?x) (?x) <> ((Num 0) + (Num ?n)) ((Num ?n)) <> ((Num ?n) + (Num 0)) ((Num ?n)) <> ((Num ?x) + (Num ?y)) ((Num @add ?x ?y)) <> (fib (Num 0)) ((Num 0)) <> (fib (Num 1)) ((Num 1)) <> (fib (Num ?n)) (defer fib (Num @sub ?n 1) + defer fib (Num @sub ?n 2)) fib (Num 12)