#!/usr/bin/env runhaskell
import Data.Char
g :: [String] -> (Bool, [String])
g ("true" : s) = (True, s)
g ("false" : s) = (False, s)
g ("if" : s) =
let (p, "then" : s') = g s
(q, "else" : s'') = g s'
(r, s''') = g s''
in (if p then q else r, s''')
f :: String -> String
f = map toLower . show . fst . g . words
main :: IO ()
main = interact $ unlines . map f . lines
Note that non-ascii characters in the above source code will be escaped (such as \x9f).