data BW = Black
	| White

data RGB = Red
	 | Green
	 | Blue

data Color > BW,RGB =
	Gray

struct Couple a =
	fst :: a
	snd :: a

struct Triple a < Couple a =
	thd :: a

struct Point =
	xpos :: Int
	ypos :: Int
	
struct CPoint < Point =
	color :: Color

data Box a =
	Box a
data Box2 a > Box a =
	Box2 a

opA :: Box Point -> Int
opB :: Box2 CPoint -> Int
opC :: Triple Point -> Int
opD :: Couple CPoint -> Int

opA = undefined
opB = undefined
opC = undefined
opD = undefined

p1 = {fst = Black; snd = White}
p2 = {fst = Black; snd = Red}
t1 = {fst = Black; snd = White; thd = White}
t2 = {fst = Black; snd = White; thd = Red}
t3 = {fst = Black; snd = Red;   thd = White}

mergetest1 f = ((f 1).xpos, (f 0).color)
mergetest2 x = case x of {Box a -> case x of {Box2 c -> (3, a.color);
                                              Box d -> (d.ypos, a.color)}}
mergetest3 x = case x of {Box2 c -> case x of {Box a -> (3, a.color)};
                          Box d -> (d.ypos, d.color)}
mergetest4 b = (opA b, opB b)
mergetest5 b = (opC b, opD b)