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POHow do I simplify the following command line options parsing code?
 

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  1. POHow do I simplify the following command line options parsing code?
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    <p>I am working on a homework manager for personal use, developing it with Haskell. I have, as a start, made the following code for parsing the commandline arguments, code which i should be easily extandable later through adding to <code>dispatch</code>. The functions themselves are dummies for testing purposes. I do, however, feel that this code can be made simpler, and more failsafe, though i cannot see how. The code is this:</p> <pre><code>module Main where import System.Environment main = getArgs &gt;&gt;= parse parse :: [String] -&gt; IO () parse [] = usage parse (file:mode:[]) = if mode == "list" then list file else case lookup mode dispatch of Just _ -&gt; putStrLn "That mode requires arguments" &gt;&gt; usage Nothing -&gt; putStrLn "Please supply a valid mode" &gt;&gt; usage parse (file:mode:args) = case lookup mode dispatch of Nothing -&gt; do case lookup file dispatch of Just _ -&gt; putStrLn "Please supply a data file" Nothing -&gt; putStrLn "Please supply a valid mode" usage Just fun -&gt; fun file args parse (file:[]) = case lookup file dispatch of Just _ -&gt; putStrLn "Please supply a datafile" &gt;&gt; usage Nothing -&gt; list file usage :: IO () usage = mapM_ putStrLn helptext helptext :: [String] helptext = ["Homework manager by Marcus Medom Ryding &lt;mrok4a@gmail.com&gt;" ,"Copyright 2013, licensed under BSD3" ,"Usage: homework filepath [mode] [arguments]"] dispatch :: [(String, String -&gt; [String] -&gt; IO ())] dispatch = [("new",new)] new :: String -&gt; [String] -&gt; IO () new file args = putStrLn ("NEW: " ++ file) &gt;&gt; mapM_ putStrLn args list :: String -&gt; IO () list file = putStrLn ("LIST: " ++ file) </code></pre>
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    1. COIf you want, I can show you how to use a command line parsing library to make your option parsing more slick. Would you be interested in that?
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      1. POHow do I simplify the following command line options parsing code?
      1. USGabriel Gonzalez
 

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