[Grace-core] Transparent Colours - Family Polymorphism in Grace?

[Andrew P. Black]

Here is what I was thinking of while we were on the conference call.  Not very different, I think.  Does this compile?

   Andrew

def Colour = object {

  method r(red) g(green) b(blue) {
      return object {
        def r = red
        def g = green
        def b = blue
        method asString {"Colour r:{r} g:{g} b:{b}"}
	 method renderOn(c) {…}
      } 
  }

  method red    { r 1 g 0 b 0 }
  method green  { r 0 g 1 b 0 }
  method blue   { r 0 g 0 b 1 }
  method yellow { r 0 g 1 b 1 }
  method white  { r 1 g 1 b 1 }
  method black  { r 0 g 0 b 0 }
  method midGrey { r 0.5 g 0.5 b 0.5)
}


def TransparentColour = object  {
  inherits Colour

  method r (red) g (green) b (blue) {
    return self.r(red) g(green) b(blue) alpha 1
    } 
  }
  method r(red) g(green) b(blue) alpha(t) {
    return object {
       inherits super.r(red) g(green) b(blue)
       def alpha = t
       method asString {"Transparent {super.asString} alpha:{alpha}"}
	method renderOn(c) {
		if alpha = 1 then 
			{super.renderOn:(c)} 
		else
			{…}
	}		
    } 
  }
}


print (Colour.yellow)
print (TransparentColour.yellow)

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