middle-number.hs

-- Filename     : middleNumber.hs
-- Version      : 1.0
-- Created on   : 10/02/2013
-- Last update  : 10/02/2013
-- Author       : Sam Jones
-- Description  : Chapter 6, designing programs in Haskell.
--                re-using the previosuly written maxThree
--                function to figure out and design a way to
--                find the middle value when given 3 integers.
--
-- Load using these commands:
--  $ ghci
--  $ :load maxFour.hs
--

maxThree :: Integer -> Integer -> Integer -> Integer
maxThree x y z = (x `max` y) `max` z

maxFour :: Integer -> Integer -> Integer -> Integer -> Integer
maxFour a b c d = maxThree a b c `max ` d

middleNumber :: Integer -> Integer -> Integer -> Integer
middleNumber x y z
    | between y x z = x
    | between x y z = y
    | otherwise = z

between :: Integer -> Integer -> Integer -> Bool
between m n p = n < p && n > m