sample "convenient main wrapper" code

Main.hs

module Main where

import NiceMain

main = nicemain go where go x y z = print $ (x && y) || z

NiceMain.hs

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE ViewPatterns #-}

module NiceMain (nicemain, IsMain) where

import System.Environment (getArgs)

nicemain :: (IsMain m) => m -> IO ()
nicemain main = do
  env <- getArgs
  mainApp env main

readMb :: Read a => String -> Maybe a
readMb (reads -> [(s, "")]) = Just s
readMb _                    = Nothing

class IsMain x where
  mainApp :: [String] -> x -> IO ()

instance (Read a, IsMain b) => IsMain (a -> b) where
  mainApp (x:xs) f = case readMb x of
    Just r  -> mainApp xs (f r)
    Nothing -> putStrLn "Argument of wrong type!"
  mainApp []     _ = putStrLn "Not enough arguments to main!"

instance IsMain (IO ()) where
  mainApp [] f = f
  mainApp _  _ = putStrLn "Too many arguments to main!"