hoproc.scm

;
; Simple example to illustrate higher order procedures
;

(define (inc x) (+ x 1))

(define (cube x) (* x x x))

(define (even? x) (= (remainder x 2) 0))

(define (identity x) x)

; Recursive procedure performing a recursive process
(define (fn identity combiner term inc a b)
  (if (> a b)
      identity
      (combiner (term a)
                (fn identity combiner term inc (inc a) b))))

; Recursive procedure performing an iterative process
(define (fn1 identity combiner term inc a b)
  (define (fn-iter combiner term inc a b result)
    (if (> a b)
        result
        (fn-iter combiner term inc (inc a) b (combiner (term a)
                                                       result))))

  (fn-iter combiner term inc a b identity))

(define (accumulate combiner null-value term inc a b)
  (fn null-value combiner term inc a b))

; Testing
(accumulate + 0 cube inc 1 3)
(accumulate * 1 cube inc 1 3)