rot13.hs

-- a, ab, abe, al, an, ana, ant, au, ay, b, ba, bag, bar, barn, bc, be, br, bs, c, cc, cf, cher, chere, cr, cs, cw, cy, d, e, ee, eg, envy, er, et, ev, ever, f, fa, ff, fn, fo, fr, ft, fur, fw, g, gh, gl, gp, gr, gum, h, ha, i, if, il, in, ing, iv, j, je, jf, jg, jm, jp, jr, js, jt, jw, k, l, m, marne, mm, mr, my, n, na, nag, nan, nh, nl, no, nor, ny, o, oe, of, on, one, onea, ont, op, or, p, pe, pf, pj, pl, pp, ps, pure, purer, q, r, rail, re, rg, ri, rire, rr, rt, s, sa, sb, se, sg, she, sj, sn, ss, st, t, tc, te, tu, ty, u, un, v, va, vat, vi, vs, vy, w, wc, we, wf, wg, wj, wr, ws, wt, wz, x, y, z, ze

module Main where
  
import Char
import Control.Applicative
import qualified Data.Set as Set
import List
  
lowerWords :: String -> [String]
lowerWords = filter (not . null) 
           . map (map toLower . filter isAlpha) 
           . words

readWords :: IO (Set.Set String)
readWords = Set.fromList . lowerWords <$> readFile "big.txt"

rot13 :: Char -> Char
rot13 c = chr (((((ord c - ord 'a')) + 13) `mod` 26) + (ord 'a'))

main :: IO ()
main = do w <- readWords
          let l = Set.toList (Set.intersection w (Set.map (map rot13) w))
          putStrLn (concat (intersperse ", " l))