; - Program 9.21, pg. 283 -

(define add1 (lambda (n) (+ 1 n)))

(define vector-generator
  ; TYPE:  (-> (-> (natural) T)
  ;            (-> (natural) (vector T))
  (lambda (gen-proc)
    (lambda (size)
      ; ENSURES: result is a new vector of elements indexed 0...size-1
      ; such that the ith element is (gen-proc i).  Note that the calls
      ; to gen-proc are made in order from 0 to size-1.
      (let ((vec (make-vector size)))
        (letrec
          ((loop ; TYPE: integer -> void
	    (lambda (i)
	      ; REQUIRES: 0 <= i <= size and for all 0 <= j < i,
	      ; (vector-ref vec j) = (gen-proc j)
	      ; MODIFIES: vec
	      ; EFFECT: initialize indexes i up to size-1
	      (if (< i size)
		  (begin
		    (vector-set! vec i (gen-proc i))
		    (loop (add1 i)))))))
          (loop 0))
        vec))))