{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE FlexibleInstances #-}


class Rectangle r1 r2 a | r1 a -> r2 a where 
    setWidth :: r1 a -> a -> r2 a
    setHeight :: r1 a -> a -> r2 a
    getWidth :: r1 a -> a
    getHeight :: r1 a -> a

class EqualAngle e where
    getNumberOfAngles :: e a -> Int
    
class (Rectangle s r a, EqualAngle s) => Square s r a where
    setSide :: s a -> a -> s a
    getSide :: s a -> a

data Sqr a = Square a
             deriving Show
data Rct a = Rectangle a a
             deriving Show

instance Square Sqr Rct a where
    setSide    _ s         = Square s
    getSide   (Square s)   = s

instance Rectangle Sqr Rct a where
    setWidth  (Square s) w = Rectangle w s
    setHeight (Square s) h = Rectangle s h
    getWidth  (Square s)   = s
    getHeight (Square s)   = s

instance EqualAngle Sqr where
    getNumberOfAngles _ =  4 
    
    
instance Rectangle Rct Rct a where
    setWidth  (Rectangle _ h) w = Rectangle w h
    setHeight (Rectangle w _) h = Rectangle w h
    getWidth  (Rectangle w _)   = w
    getHeight (Rectangle _ h)   = h

square rect = (getWidth rect) * (getHeight rect)

data (Num a) => Rectangle a = Rectangle a a
                            | Square a
    
setWidth (Rectangle _ h) w = Rectangle w h
setWidth (Square s) w = Rectangle w s
setHeight (Rectangle w _) h = Rectangle w h
setHeight (Square s) h = Rectangle s h

getWidth (Rectangle w _) = w
getWidth (Square s) = s
getHeight (Rectangle _ h) = h
getHeight (Square s) = s


square r = (getWidth r) * (getHeight r)  

setSide (Rectangle _ _) s = Square s
setSide (Square _) s = Square s

data (Num a) => Rectangle a = Rectangle a a
                            | Square a
    
setWidth (Rectangle _ h) w | w == h = Square w
                           | otherwise Rectangle w h
setWidth (Square s) w | w == s = Square w
                      | otherwise Rectangle w s
setHeight (Rectangle w _) h | w == h = Square w
                            | otherwise Rectangle w h
setHeight (Square s) h | s == h = Square s
                       | otherwise Rectangle s h

getWidth (Rectangle w _) = w
getWidth (Square s) = s
getHeight (Rectangle _ h) = h
getHeight (Square s) = s

setSide (Rectangle _ _) s = Square s
setSide (Square _) s = Square s

square r = (getWidth r) * (getHeight r)