Options.Harg.Construct

Documentation

option :: OptReader a -> (OptionOpt '[] a -> OptionOpt attr b) -> Opt b

Create an option parser, equivalent to option. The second argument is the modifiers to add to the option, and can be defined by using function composition (.).

  someOption :: Opt Int
  someOption
    = option readParser
        ( long "someopt"
        . help "Some option"
        . defaultVal 256
        )

flag

Arguments

:: a

Default value

-> a

Active value

-> (FlagOpt '[] a -> FlagOpt attr b)

-> Opt b

Create a flag parser, equivalent to option. The first argument is the default value (returned when the flag modifier is absent), and the second is the active value (returned when the flag modifier is present). The second argument is the modifiers to add to the option, and can be defined by using function composition (.).

  someFlag :: Opt Int
  someFlag
    = flag 0 1
        ( long "someflag"
        . help "Some flag"
        )

switch :: (FlagOpt '[] Bool -> FlagOpt attr Bool) -> Opt Bool

A flag parser, specialized to Bool. The parser (e.g. when parsing an environment variable) will accept true and false, but case insensitive, rather than using the Read instance for Bool. The default value is False, and the active value is True.

  someSwitch :: Opt Bool
  someSwitch
    = switch
        ( long "someswitch"
        . help "Some switch"
        )

switch' :: (FlagOpt '[] Bool -> FlagOpt attr Bool) -> Opt Bool

Similar to switch, but the default value is True and the active is False.

argument :: OptReader a -> (ArgumentOpt '[] a -> ArgumentOpt attr b) -> Opt b

Create an argument parser, equivalent to argument. The second argument is the modifiers to add to the option, and can be defined by using function composition (.).

  someArgument :: Opt Int
  someArgument
    = argument
        ( help "Some argument"
        . defaultVal "this is the default"
        )

long :: HasLong o attr => String -> o attr a -> o attr a

Add a long modifier to an option

short :: HasShort o attr => Char -> o attr a -> o attr a

Add a short modifier to an option

help :: HasHelp o attr => String -> o attr a -> o attr a

Add help to an option

metavar :: HasMetavar o attr => String -> o attr a -> o attr a

Add a metavar metavar to an option, to be displayed as the meta-parameter next to long/short modifiers

envVar :: HasEnvVar o attr => String -> o attr a -> o attr a

Specify an environment variable to lookup for an option

defaultVal :: (HasDefaultVal o attr, NotInAttrs OptDefault attr (DuplicateAttrMultipleErr "defaultVal" '["defaultStr", "required"]), NotInAttrs OptOptional attr (IncompatibleAttrsErr "defaultVal" "optional")) => a -> o attr a -> o (OptDefault ': attr) a

Add a default value to an option. Cannot be used in conjuction with with required, defaultStr or optional.

defaultStr :: (HasDefaultStr o attr, NotInAttrs OptDefault attr (DuplicateAttrMultipleErr "defaultStr" '["defaultVal", "required"]), NotInAttrs OptOptional attr (IncompatibleAttrsErr "defaultStr" "optional")) => String -> o attr a -> o (OptDefault ': attr) a

Add a default unparsed value to an option. Cannot be used in conjuction with defaultVal, required or optional.

required :: (HasRequired o attr, NotInAttrs OptDefault attr (DuplicateAttrMultipleErr "required" '["defaultVal", "defaultStr"]), NotInAttrs OptOptional attr (IncompatibleAttrsErr "required" "optional")) => o attr a -> o (OptDefault ': attr) a

Mark an option as required. Cannot be used in conjunction with optional, defaultVal or requiredStr.

optional :: (HasOptional o attr, NotInAttrs OptOptional attr (DuplicateAttrErr "optional"), NotInAttrs OptDefault attr (IncompatibleAttrsErr "optional" "defaultVal")) => o attr a -> o (OptOptional ': attr) (Maybe a)

Specify that an option is optional. This will convert an Opt a to an Opt (Maybe a). Cannot be used in conjunction with defaultVal, defaultStr or required.

parseWith

Arguments

:: (String -> Maybe a)

Original parser

-> String -> Either String a

Convert a parser that returns Maybe to a parser that returns Either, with the default Left value unable to parse: <input>.

readParser :: Read a => OptReader a

A parser that uses the Read instance to parse into a type.

strParser :: IsString s => String -> Either String s

A parser that returns a string. Any type that has an instance of IsString will work, and this parser always succeeds.

boolParser :: String -> Either String Bool

A parser that returns a Bool. This will succeed for the strings true and false in a case-insensitive manner.

manyParser

Arguments

:: String

Separator

-> OptReader a

Parser for each string

-> OptReader [a]

A parser that can parse many items, returning a list.