module Week03 where

import Char -- need this if you want to
            -- use Char.ord or Char.chr

factorial :: Integer -> Integer
factorial n
   | n==0      = 1
   | otherwise = n * (factorial (n - 1))

wordLength :: String -> Int
wordLength word
  | word == ""  = 0
  | otherwise   = 1 + (wordLength (tail word))

-- tested by test 3
isIn :: String -> [String] -> Bool
isIn key list
   | list == []          = False
   | key == firstElement = True
   | otherwise           = isIn key rest
   where
      firstElement = head list
      rest         = tail list 

-- only works with pos numbers or 0
-- use test case 4
integer2digits :: Integer -> [Integer]
integer2digits number
   | number < 10 = [number]
   | otherwise   = leadingDigits++[lastDigit]
   where
      lastDigit     = number `mod` 10
      leadingDigits = integer2digits (number `div` 10)  

test :: Int -> Bool
test 3 
   | (isIn "at" ["Strange","er","than","fiction"]) /= False = False
   | (isIn "at" ["at","er","than","fiction"])      /= True  = False
   | (isIn "at" [])                                /= False = False
   | (isIn "at" ["Strange","at","than","fiction"]) /= True  = False
   | (isIn ""   ["Strange","at","than","fiction"]) /= False = False
   | otherwise                                              = True

test 4
   | (integer2digits 42) /= [4,2] = False
   | (integer2digits 0)  /= [0]   = False
   | otherwise                    = True



{-
Imperial to Metric

You wish to convert heights in feet and inches to
metres. Unfortunately you remember that there are
exactly 25.4 millimetres in an inch and 12 inches
in a foot.

Write a function imperial2m to do this conversion.

-}
imperial2m :: Float -> Float -> Float

















imperial2m a b = (a*12+b)*0.0254

















{-
-- function to convert feet and inches
-- to metres
imperial2m :: Float -> Float -> Float
imperial2m feet inches = metres
  where
     metres        = totalInches * metersPerInch
     totalInches   = inches + (feet*inchesPerFoot)
     metersPerInch = mmPerInch / mmPerMetre
     inchesPerFoot = 12
     mmPerMetre    = 1000
     mmPerInch     = 25.4
-}