Safe Haskell	Safe-Inferred

System.Console.Argument

Contents

Option descriptions
Argument types

Description

This module contains functions to create option descriptions, together with their argument types.

Synopsis

Option descriptions

data Option a Source

A value of type Option a describes an option, that delivers a value to the program of type a.

option Source

Arguments

:: [Char]	List of short option characters.
-> [String]	List of long option strings.
-> Type a	Type of option argument.
-> a	Default value.
-> String	Description.
-> Option a	The resulting option description.

Create an option description.

Options can have arguments, as in myprogram --foo=bar, where bar is the argument to foo. These arguments have types, dictated by the particular option; this type is the third parameter to option.

data Type a Source

A Type a represents the type of an option or argument.

Further below you can find some common types of option arguments.

Constructors

Type
Fields parser :: String -> Either String a Parse the option argument into a value (`Right`) or signal a parsing error (`Left`). name :: String A name for this type of option argument (for usage info). defaultValue :: Maybe a The default value, when the option occurs without option argument. `Nothing` means that an argument is required for this type of option.