implementation module support

import StdEnv, StdIO
	
toPoint2				:: Size Pos -> Point2
toPoint2 {w,h} {rx,ry}	= {x=toInt ((toReal w)*rx),y=toInt ((toReal h)*ry)}

fromPoint2				:: Size Point2 -> Pos
fromPoint2 {w,h} {x,y}	= {rx=(toReal x)/(toReal w),ry=(toReal y)/(toReal h)}

circle	 				:: Int -> Oval
circle r				= {oval_rx=r,oval_ry=r}

instance zero Pos where
	zero				= {rx=zero,ry=zero}
instance zero Vel where
	zero				= {v0=zero,v1=zero}
instance + Pos where
	(+) p1 p2			= {rx=p1.rx+p2.rx,ry=p1.ry+p2.ry}
instance - Pos where
	(-) p1 p2			= {rx=p1.rx-p2.rx,ry=p1.ry-p2.ry}
instance + Vel where
	(+) a b				= {v0=a.v0+b.v0,v1=a.v1+b.v1}
instance - Vel where
	(-) a b				= {v0=a.v0-b.v0,v1=a.v1-b.v1}

class scale a			:: !Real !a -> a

instance scale Pos where
	scale r p			= {rx=r*p.rx,ry=r*p.ry}
instance scale Vel where
	scale r v			= {v0=r*v.v0,v1=r*v.v1}

class toVel a			:: !a -> Vel

instance toVel Pos where
	toVel p				= {v0=p.rx,v1=p.ry}

class dist a			:: !a !a -> Real

instance dist Pos where
	dist p1 p2		= sqrt ((p1.rx - p2.rx)^2.0 + (p1.ry - p2.ry)^2.0)
instance dist Real where
	dist r1 r2		= abs (r1 - r2)

movePos				:: Vel Pos -> Pos
movePos v p			= {p & rx=p.rx+v.v0,ry=p.ry+v.v1}