compile.hs

import System.Cmd (system)
import System.Environment (getArgs)
import Data.Text (breakOn, pack, unpack)
import Data.Maybe (fromJust)

compilers = [
              (".hs", "ghc"),
              (".c", "make")
            ]

main = do
  args <- getArgs
  if null args
    then error "no input filename"
    else do
      let (mod, ext) = breakOn (pack ".") $ pack $ head args
      let mod' = unpack mod
      let ext' = unpack ext
      if null ext'
        then error "no extension"
        else do
          let compiler = fromJust $ lookup ext' compilers
          let command = unwords [compiler, mod']
          putStrLn command
          system command