Haskell: Parsing command line arguments

Question

This more of a style question, rather than a how to.

So I\'ve got a program that needs two command line arguments: a string and an integer.

I implemented it this

Answer 1

These days, I'm a big fan of optparse-generic for parsing command line arguments:

• it lets you parse arguments (not just options)
• it lets you parse options (not just arguments)
• you can annotate the arguments to provide a useful help
• but you don't have to

As your program matures, you may want to come up with a complete help, and a well-annotated options data type, which options-generic is great at. But it's also great at parsing lists and tuples without any annotation at all, so you can hit the ground running:

For example

{-# LANGUAGE OverloadedStrings #-}
module Main where

import Options.Generic

main :: IO ()
main = do
  (n, c) <- getRecord "Example program"
  putStrLn $ replicate n c

Runs as:

$ ./OptparseGenericExample
Missing: INT CHAR

Usage: OptparseGenericExample INT CHAR
$ ./OptparseGenericExample 5 c
ccccc