Options.Applicative.Common

Option parsers

A Parser is composed of a list of options. Several kinds of options are supported:

• Flags: simple no-argument options. When a flag is encountered on the command line, its value is returned.
• Options: options with an argument. An option can define a reader, which converts its argument from String to the desired value, or throws a parse error if the argument does not validate correctly.
• Arguments: positional arguments, validated in the same way as option arguments.
• Commands. A command defines a completely independent sub-parser. When a command is encountered, the whole command line is passed to the corresponding parser.

data Parser a

A Parser a is an option parser returning a value of type a.

Instances

Functor Parser

Applicative Parser

Alternative Parser

liftOpt :: Option a -> Parser a

Create a parser composed of a single option.

Program descriptions

data ParserInfo a

A full description for a runnable Parser for a program.

Constructors

ParserInfo

Fields

infoParser :: Parser a

the option parser for the program

infoFullDesc :: Bool

whether the help text should contain full documentation

infoProgDesc :: String

brief parser description

infoHeader :: String

header of the full parser description

infoFooter :: String

footer of the full parser description

infoFailureCode :: Int

exit code for a parser failure

Instances

Functor ParserInfo

Running parsers

runParser :: MonadP m => Parser a -> [String] -> m (a, [String])

Apply a Parser to a command line, and return a result and leftover arguments. This function returns an error if any parsing error occurs, or if any options are missing and don't have a default value.

runParserFully :: MonadP m => Parser a -> [String] -> m a

evalParser :: Parser a -> Maybe a

The default value of a Parser. This function returns an error if any of the options don't have a default value.

Low-level utilities

mapParser :: (forall x. OptHelpInfo -> Option x -> b) -> Parser a -> [b]

Map a polymorphic function over all the options of a parser, and collect the results in a list.

treeMapParser :: (forall x. OptHelpInfo -> Option x -> b) -> Parser a -> OptTree b

Like mapParser, but collect the results in a tree structure.

optionNames :: OptReader a -> [OptName]