Shapes module

shapes.hs

module Shapes
( Point(..)  
, Shape(..)  
, surface  
, nudge  
, baseCircle  
, baseRect  
) where  

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

surface :: Shape -> Float  
surface (Circle _ r) = pi * r ^ 2  
surface (Rectangle (Point x1 y1) (Point x2 y2)) = (abs $ x2 - x1) * (abs $ y2 - y1)  

nudge :: Shape -> Float -> Float -> Shape  
nudge (Circle (Point x y) r) a b = Circle (Point (x+a) (y+b)) r  
nudge (Rectangle (Point x1 y1) (Point x2 y2)) a b = Rectangle (Point (x1+a) (y1+b)) (Point (x2+a) (y2+b))

baseCircle :: Float -> Shape  
baseCircle r = Circle (Point 0 0) r  
  
baseRect :: Float -> Float -> Shape  
baseRect width height = Rectangle (Point 0 0) (Point width height)