fib.untyped

nil = \x x
cons = \x \y \f f x y
car = \x \y x
cdr = \x \y y

true = \x \y x
false = \x \y y
if = \b \t \e b t e

zero = \f \x x
succ = \n \f \x f (n f x)
pred = \n \f \x n (\g \h h (g f)) (\u x) (\u u)
is_zero = \n n (\x false) true
plus = \m \n m succ n

c_to_n = \n n (\x +<1, x>) 0

fib = \f \n \a if (is_zero n) (a car) (f f (pred n) (cons (plus (a car) ((a cdr) car)) (cons (a car) nil)))

print (c_to_n (fib fib (succ (succ (succ (succ zero)))) (cons (succ zero) (cons zero nil))))