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

Methods

fmap :: (a -> b) -> Parser a -> Parser b

(<$) :: a -> Parser b -> Parser a

Applicative Parser

Methods

pure :: a -> Parser a

(<*>) :: Parser (a -> b) -> Parser a -> Parser b

(*>) :: Parser a -> Parser b -> Parser b

(<*) :: Parser a -> Parser b -> Parser a

Alternative Parser

Methods

empty :: Parser a

(<|>) :: Parser a -> Parser a -> Parser a

some :: Parser a -> Parser [a]

many :: Parser a -> Parser [a]

liftOpt :: Option a -> Parser a

Create a parser composed of a single option.

showOption :: OptName -> String

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 :: Chunk Doc

  brief parser description

• infoHeader :: Chunk Doc

  header of the full parser description

• infoFooter :: Chunk Doc

  footer of the full parser description

• infoFailureCode :: Int

  exit code for a parser failure

• infoPolicy :: ArgPolicy

  allow regular options and flags to occur after arguments (default: InterspersePolicy)

Instances

Functor ParserInfo

Methods

fmap :: (a -> b) -> ParserInfo a -> ParserInfo b

(<$) :: a -> ParserInfo b -> ParserInfo a

data ParserPrefs

Global preferences for a top-level Parser.

Constructors

ParserPrefs

Fields

• prefMultiSuffix :: String

  metavar suffix for multiple options

• prefDisambiguate :: Bool

  automatically disambiguate abbreviations (default: False)

• prefShowHelpOnError :: Bool

  always show help text on parse errors (default: False)

• prefShowHelpOnEmpty :: Bool

  show the help text for a command or subcommand if it fails with no input (default: False)

• prefBacktrack :: Bool

  backtrack to parent parser when a subcommand fails (default: True)

• prefColumns :: Int

  number of columns in the terminal, used to format the help page (default: 80)

Instances

Eq ParserPrefs

Methods

(==) :: ParserPrefs -> ParserPrefs -> Bool

(/=) :: ParserPrefs -> ParserPrefs -> Bool

Show ParserPrefs

Methods

showsPrec :: Int -> ParserPrefs -> ShowS

show :: ParserPrefs -> String

showList :: [ParserPrefs] -> ShowS

Running parsers

runParserInfo :: MonadP m => ParserInfo a -> Args -> m a

runParserFully :: MonadP m => ArgPolicy -> Parser a -> Args -> m a

runParser :: MonadP m => ArgPolicy -> IsCmdStart -> Parser a -> Args -> m (a, Args)

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.

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]