-- ColCalc.hs
--
-- Convert integer values to Excel column names
--
-- E.g. 1 -> A, 2 -> B, 27 -> AA, 52 -> AZ etc.
--
module ColCalc (intToCol) where

import Data.List
import Data.Char

intToCol       :: Int -> String
intToCol n     = reverse $ unfoldr step n
  where step x | x == 0         = Nothing
               | otherwise      = Just (toAscii (x `mod` 26), (x - 1) `div` 26)
        toAscii i               = chr $ (if i == 0 then 26 else i) + 64