shape1.hs

data Point = Point Float Float deriving (Show)
data Shape = Circle Point Float | Rectangle Point Point deriving (Show)

area::Shape->Float

area (Circle _ r) = pi * r^2
area (Rectangle (Point x1 y1) (Point x2 y2)) = (abs $ x2 -x1)*(abs $ y2-y1)

main = do
  -- fun $ x... is the same as fun(x...)
	print $ area $ Circle (Point 1 2) 5