;; usefuls.scm
;; Useful functions and examples for final projects

;; Input-loop defines a simple user input cycle
;; that can easily be extended to whatever purpose
;; you'd like.
(define (input-loop)
  (display "> ")
  (let ((user-input (read-line)))
    (cond ((null? user-input)
	   (input-loop))
	  ((equal? (car user-input) 'quit)
	   (show "Bye!"))
	  (else
	   (begin
	     (display "User input was: ")
	     (display user-input)
	     (newline)
	     (input-loop))))))


;; Returns the hexadecimal string representation of
;; the color defined by the three integers as argument
;; (create-color 255 0 0) is pure red,
;; (create-color 255 0 255) is pure purple, et cetera.
(define (create-color red green blue)
  (define (hex-digit num)
    (let ((str-rep (number->string num 16)))
      (if (= (string-length str-rep) 1)
	  (string-append "0" str-rep)
	  str-rep)))
  (define (bound num)
    (min 255 (max num 0)))
  (let ((red (bound red))
	(blue (bound blue))
	(green (bound green)))
  (apply string-append
	 (cons "#" (map hex-digit `(,red ,green ,blue))))))