name: optparse-applicative version: 0.9.1.2 synopsis: Utilities and combinators for parsing command line options description: Here is a simple example of an applicative option parser: . @ data Sample = Sample { hello :: String , quiet :: Bool } . sample :: Parser Sample sample = Sample \<$\> strOption ( long \"hello\" \<\> metavar \"TARGET\" \<\> help \"Target for the greeting\" ) \<*\> switch ( long \"quiet\" \<\> help \"Whether to be quiet\" ) @ . The parser is built using applicative style starting from a set of basic combinators. In this example, @hello@ is defined as an 'option' with a @String@ argument, while @quiet@ is a boolean 'flag' (called 'switch'). . A parser can be used like this: . @ greet :: Sample -> IO () greet (Sample h False) = putStrLn $ \"Hello, \" ++ h greet _ = return () . main :: IO () main = execParser opts \>\>= greet where opts = info (helper \<*\> sample) ( fullDesc \<\> progDesc \"Print a greeting for TARGET\" \<\> header \"hello - a test for optparse-applicative\" ) @ . The @greet@ function is the entry point of the program, while @opts@ is a complete description of the program, used when generating a help text. The 'helper' combinator takes any parser, and adds a @help@ option to it (which always fails). . The @hello@ option in this example is mandatory (since it doesn't have a default value), so running the program without any argument will display a help text: . >hello - a test for optparse-applicative > >Usage: hello --hello TARGET [--quiet] > Print a greeting for TARGET > >Available options: > -h,--help Show this help text > --hello TARGET Target for the greeting > --quiet Whether to be quiet . containing a short usage summary, and a detailed list of options with descriptions. license: BSD3 license-file: LICENSE author: Paolo Capriotti maintainer: p.capriotti@gmail.com copyright: (c) 2012 Paolo Capriotti