;;; FIBC -- FIB using first-class continuations, written by Kent Dybvig

(library (rnrs-benchmarks fibc)
  (export main)
  (import (rnrs) (rnrs-benchmarks))
  
  (define (_1+ n) (+ n 1))
  (define (_1- n) (- n 1))
  
  ;;; fib with peano arithmetic (using numbers) with call/cc
  
  (define (addc x y k)
    (if (zero? y)
      (k x)
      (addc (_1+ x) (_1- y) k)))
  
  (define (fibc x c)
    (if (zero? x)
      (c 0)
      (if (zero? (_1- x))
        (c 1)
        (addc (call-with-current-continuation (lambda (c) (fibc (_1- x) c)))
              (call-with-current-continuation (lambda (c) (fibc (_1- (_1- x)) c)))
              c))))
  
  (define (main)
    (run-benchmark
      "fibc"
      fibc-iters
      (lambda (result) (equal? result 2584))
      (lambda (x c) (lambda () (fibc x c)))
      18
      (lambda (n) n))))