; fib.ss
; SICP section 1.2.2
; Chris Parrish

; tree recursion

(define fib
  (lambda (n)
    (cond ((= 0 n) 0)
          ((= 1 n) 1)
          (else (+ (fib (- n 1))
                   (fib (- n 2)))))))
(trace fib)

(fib 5)

; cf. SICP fig. 1.5, page 38