;;; This file contains programs from ch9.ss that work with
;;; any representation of vectors; including the built-in one of Scheme.
;;; For that reason make-vector is not defined here

; - Program 9.1, pg. 269 -

(define view 
  (lambda (vec) 
    (let ((highest-index (sub1 (vector-length vec)))) 
      (letrec ((loop (lambda (i) 
                       (display (vector-ref vec i)) 
                       (if (< i highest-index) 
                           (begin
                             (display " ") 
                             (loop (add1 i))))))) 
        (display "#(") 
        (loop 0) 
        (display ")")
	(newline)))))

; - End Program -


; - Program 9.3, pg. 271 -

(define list->vector 
  (lambda (ls) 
    ((vector-generator (lambda (i) (list-ref ls i))) (length ls))))

; - End Program -

; - Program 9.4, pg. 271 -

(define vector 
  (lambda args
    (list->vector args)))

; - End Program -

; - Program 9.5, pg. 272 -

(define vector-stretch
  (lambda (vec new-size) 
    (let ((size (vector-length vec))) 
      (let ((gen-proc (lambda (i) 
                        (if (< i size) 
                            (vector-ref vec i) 
                            '()))))
        ((vector-generator gen-proc) new-size)))))

; - End Program -

; - Program 9.6, pg. 272 -

(define vector-copy
  (lambda (vec) 
    (vector-stretch vec (vector-length vec))))

; - End Program -

; - Program 9.7, pg. 272 -

(define vector-update
  (lambda (vec k val) 
    (let ((gen-proc (lambda (i) 
                      (if (= i k) 
                          val
                          (vector-ref vec i))))) 
      ((vector-generator gen-proc) (vector-length vec)))))

; - End Program -

; - Program 9.8, pg. 273 -

(define list->vector
  (lambda (ls) 
    (let ((vec (make-vector (length ls)))) 
      (letrec 
        ((convert (lambda (ls* v i) 
                    (if (null? ls*) 
                        v 
                        (let ((new-v (vector-update v i (car ls*))))
                          (convert (cdr ls*) new-v (add1 i))))))) 
        (convert ls vec 0)))))

; - End Program -

; - Program 9.9, pg. 273 -

(define vector-map
  (lambda (proc vec) 
    ((vector-generator (lambda (i) (proc (vector-ref vec i)))) 
     (vector-length vec))))

; - End Program -

; - Program 9.10, pg. 274 -

(define multiply-by-scalar 
  (lambda (c vec) 
    (vector-map (lambda (elem) (* c elem)) vec)))

; - End Program -

; - Program 9.11, pg. 274 -

(define vector-apply-elementwise-to-both 
  (lambda (proc) 
    (lambda (vec1 vec2) 
      (let ((gen-proc 
              (lambda (i) 
                (proc (vector-ref vec1 i) (vector-ref vec2 i))))) 
        ((vector-generator gen-proc) (vector-length vec1))))))

; - End Program -

; - Program 9.12, pg. 275 -

(define vec+ (vector-apply-elementwise-to-both +))

(define vec* (vector-apply-elementwise-to-both *)) 

; - End Program -

; - Program 9.13, pg. 275 -

(define vector-sum
  (lambda (vec) 
    (let ((size (vector-length vec))) 
      (letrec 
        ((helper
           (lambda (i) 
             (if (= i size) 
                 0 
                 (+ (vector-ref vec i) (helper (add1 i))))))) 
        (helper 0)))))

; - End Program -

; - Program 9.14, pg. 276 -

(define vector-product 
  (lambda (vec) 
    (let ((size (vector-length vec)))
      (letrec 
        ((helper 
           (lambda (i) 
             (if (= i size) 
                 1 
                 (* (vector-ref vec i) (helper (add1 i))))))) 
        (helper 0)))))

; - End Program -

; - Program 9.15, pg. 277 -

(define vector-accumulate 
  (lambda (proc seed) 
    (lambda (vec) 
      (let ((size (vector-length vec))) 
        (letrec 
          ((helper 
             (lambda (i) 
               (if (= i size)
                   seed 
                   (proc (vector-ref vec i) (helper (add1 i))))))) 
          (helper 0))))))

; - End Program -

; - Program 9.16, pg. 277 -

(define vector->list (vector-accumulate cons '()))

; - End Program -

; - Program 9.17, pg. 279 -

(define dot-product 
  (lambda (vec1 vec2) 
    (let ((size (vector-length vec1))) 
      (letrec 
        ((loop 
           (lambda (i acc) 
             (if (= i size) 
                 acc 
                 (loop (add1 i) 
                       (+ acc (* (vector-ref vec1 i) 
                                 (vector-ref vec2 i)))))))) 
        (loop 0 0)))))

; - End Program -