barcode.hs

module Main where

import System.Random
import Data.Maybe
import Data.Bits
import Data.List
import Data.Char
 
main = do
  gen <- getStdGen
  print $ nub $ take 1000 $ barcodes avail_chrs 8 (randomRs (0,maxBound::Int) gen :: [Int])

avail_chrs :: [Char]
avail_chrs = filter (/= 'O') ['A'..'Z']

barcodes :: [Char] -> Int -> [Int] -> [[Char]]
barcodes comps len ns = (map (avail_chrs !!) (seg ++ [check_digit])) : barcodes comps len segs
	where

    seg = map (flip mod $ length avail_chrs) $ take (len-1) ns
    segs = drop (len-1) ns
    check_digit = get_check_digit (length avail_chrs) seg
    
    get_check_digit :: Int -> [Int] -> Int
    get_check_digit max = flip mod max . foldl1 xor

unique :: (Eq a) => [a] -> [a]
unique [] = []
unique (x:xs)
  | x `elem` xs = unique xs
  | otherwise   = x: unique xs