Automatic Memoization with Closures

memoize.scm

;; make a function that caches its past results
(define (memoize proc)
  (let ((cache (make-table)))
    (define (delegate . args)
      (let ((hit (lookup cache args)))
        (or hit ; or miss
            (let ((result (apply proc args)))
              (insert! cache args result)
              result))))
    delegate))

;; GUILE specific
(define make-table make-hash-table)
(define lookup hash-ref)
(define insert! hash-set!)

;; usage example
(define memo-fib
  (memoize (lambda (n)
             (cond ((= n 0) 0)
                   ((= n 1) 1)
                   (else (+ (memo-fib (- n 1))
                            (memo-fib (- n 2))))))))