; A color is one of the following:
; - 'green
; - 'red
; - 'violet
; - 'yellow
; - 'orange
; - 'blue

; Color examples:
; 'green
; 'red
; 'violet
; 'yellow
; 'orange
; 'blue


; The "template" for any function on a color is
; color_func : color -> ...
; (define (color_func a_color)
;   (cond
;      [(symbol=? color 'green)  ...]
;      [(symbol=? color 'red)    ...]
;      [(symbol=? color 'violet) ...]
;      [(symbol=? color 'yellow) ...]
;      [(symbol=? color 'orange) ...]
;      [(symbol=? color 'blue)   ...]))


; color-complement : color -> color
;
; Purpose: Returns the name of the color complementary to the
; input color.

(define (color-complement color)
   (cond
      [(symbol=? color 'green)  'red]
      [(symbol=? color 'red)    'color]
      [(symbol=? color 'violet) 'yellow]
      [(symbol=? color 'yellow) 'violet]
      [(symbol=? color 'orange) 'blue]
      [(symbol=? color 'blue)   'orange]))

"Test color-complement:"
(symbol=? (color-complement 'green)  'red)
(symbol=? (color-complement 'red)    'green)
(symbol=? (color-complement 'yellow) 'violet)
(symbol=? (color-complement 'violet) 'yellow)
(symbol=? (color-complement 'orange) 'blue)
(symbol=? (color-complement 'blue)   'orange)



; color-primary? : color -> boolean
: Returns whether the color is a primary color or not.

(define (color-primary? color)
   (cond
      [(symbol=? color 'green)  false]
      [(symbol=? color 'red)    true]
      [(symbol=? color 'violet) false]
      [(symbol=? color 'yellow) false]
      [(symbol=? color 'orange) false]
      [(symbol=? color 'blue)   true]))

"Test color-primary?:"
(boolean=? (color-primary? 'green)  false)
(boolean=? (color-primary? 'red)    true)
(boolean=? (color-primary? 'yellow) false)
(boolean=? (color-primary? 'violet) false)
(boolean=? (color-primary? 'orange) false)
(boolean=? (color-primary? 'blue)   true)