System.Console.ArgParser.Params

Parameters are basic building blocks of a command line parser.

Standard constructors

Constructor

data StdArgParam a

Defines a parameter consuming arguments on the command line. The source defines whether the arguments are positional:

myprog posarg1 posarg2 ...

... or are taken from a flag:

myprog --myflag flagarg1 flagarg2 ...

short form:

myprog -m flagarg1 flagarg2 ...

One can provide two signatures of parsing function using the 'ArgParser type':

• SingleArgParser means that the parameter expect exactly one arg
• MulipleArgParser means that the parameter expect any number of args

Constructors

StdArgParam (Optionality a) ArgSrc Key (ArgParser a)

Instances

ParamSpec StdArgParam

Misc types

data ArgSrc

Defines the source of a parameter: either positional or flag.

Constructors

Flag

Pos

data FlagFormat

Specify the format of a flag

Constructors

Short

Possible short format ie -f or --foo

Long

Only long format ie --foo

data ArgParser a

Defines the number of args consumed by a standard parameter

Constructors

SingleArgParser (Arg -> ParseResult a)

Uses exactly one arg

MulipleArgParser (Args -> ParseResult a)

Uses any number of args

data Optionality a

Defines whether a parameter is mandatory or optional. When a parameter is marked as Optional, a default value must be provided.

Constructors

Mandatory

Optional a

type Key = String

identifier used to specify the name of a flag or a positional argument.

Special constructors

data FlagParam a

A simple command line flag. The parsing function will be passed True if the flag is present, if the flag is provided to the command line, and False otherwise. For a key foo, the flag can either be --foo or -f

Constructors

FlagParam FlagFormat Key (Bool -> a)

Instances

ParamSpec FlagParam

data Descr spec a infixl 2

Allows the user to provide a description for a particular parameter. Can be used as an infix operator:

myparam `Descr` "this is my description"

Constructors

Descr infixl 2

Fields

getdvalue :: spec a

getuserdescr :: String

Instances

ParamSpec spec => ParamSpec (Descr spec)

data MetaVar spec a infixl 2

Allows the user to provide a description for a particular parameter. Can be used as an infix operator:

myparam `Descr` "this is my description"

Constructors

MetaVar infixl 2

Fields

getmvvalue :: spec a

getusermvar :: String

Instances

ParamSpec spec => ParamSpec (MetaVar spec)