Safe Haskell	None
Language	Haskell98

System.Console.CmdArgs.Implicit

Contents

Running command lines
Constructing command lines
- Impure
- Pure
Re-exported for convenience

Description

This module provides simple command line argument processing. The main function of interest is cmdArgs. A simple example is:

data Sample = Sample {hello :: String} deriving (Show, Data, Typeable)

sample = Sample{hello = def &= help "World argument" &= opt "world"}
         &= summary "Sample v1"

main = print =<< cmdArgs sample

Attributes are used to control a number of behaviours:

The help message: help, typ, details, summary, program, groupname
Flag behaviour: opt, enum, verbosity, ignore
Flag name assignment: name, explicit
Controlling non-flag arguments: args, argPos
- multi-mode programs: modes, auto
Supported Types: Each field in the record must be one of the supported atomic types (String, Int, Integer, Float, Double, Bool, an enumeration, a tuple of atomic types) or a list ([]) or Maybe wrapping at atomic type.
Missing Fields: If a field is shared by multiple modes, it may be omitted in subsequent modes, and will default to the previous value.
Purity: Values created with annotations are not pure - the first time they are computed they will include the annotations, but subsequently they will not. If you wish to run the above example in a more robust way:
```
sample = cmdArgsMode $ Sample{hello = ... -- as before
```
```
main = print =<< cmdArgsRun sample
```
Even using this scheme, sometimes GHC's optimisations may share values who have the same annotation. To disable sharing you may need to specify {-# OPTIONS_GHC -fno-cse #-} in the module you define the flags.
Pure annotations: Alternatively, you may use pure annotations, which are referentially transparent, but less type safe and more verbose. The initial example may be written as:
sample = record Sample{} [hello := def += help "World argument" += opt "world"] += summary "Sample v1"
```
main = print =<< (cmdArgs_ sample :: IO Sample)
```
All the examples are written using impure annotations. To convert to pure annotations follow the rules:
```
Ctor {field1 = value1 &= ann1, field2 = value2} &= ann2 ==> record Ctor{} [field1 := value1 += ann1, field2 := value2] += ann2
Ctor (value1 &= ann1) value2 &= ann2 ==> record Ctor{} [atom value1 += ann1, atom value2] += ann2
modes [Ctor1{...}, Ctor2{...}] ==> modes_ [record Ctor1{} [...], record Ctor2{} [...]]
Ctor {field1 = enum [X &= ann, Y]} ==> record Ctor{} [enum_ field1 [atom X += ann, atom Y]]
```
If you are willing to use TemplateHaskell, you can write in the impure syntax, but have your code automatically translated to the pure style. For more details see System.Console.CmdArgs.Quote.

Synopsis

Running command lines

cmdArgs :: Data a => a -> IO a Source

Take impurely annotated records and run the corresponding command line. Shortcut for cmdArgsRun . cmdArgsMode.

To use cmdArgs with custom command line arguments see withArgs.

cmdArgsMode :: Data a => a -> Mode (CmdArgs a) Source

Take impurely annotated records and turn them in to a Mode value, that can make use of the System.Console.CmdArgs.Explicit functions (i.e. process).

Annotated records are impure, and will only contain annotations on their first use. The result of this function is pure, and can be reused.

cmdArgsRun :: Mode (CmdArgs a) -> IO a Source

Run a Mode structure. This function reads the command line arguments and then performs as follows:

If invalid arguments are given, it will display the error message and exit.
If --help is given, it will display the help message and exit.
If --version is given, it will display the version and exit.
In all other circumstances the program will return a value.
Additionally, if either --quiet or --verbose is given (see verbosity) it will set the verbosity (see setVerbosity).

cmdArgs_ :: Data a => Annotate Ann -> IO a Source

Take purely annotated records and run the corresponding command line. Shortcut for cmdArgsRun . cmdArgsMode_.

To use cmdArgs_ with custom command line arguments see withArgs.

cmdArgsMode_ :: Data a => Annotate Ann -> Mode (CmdArgs a) Source

Take purely annotated records and turn them in to a Mode value, that can make use of the System.Console.CmdArgs.Explicit functions (i.e. process).

cmdArgsApply :: CmdArgs a -> IO a Source

Perform the necessary actions dictated by a CmdArgs structure.

If cmdArgsHelp is Just, it will display the help message and exit.
If cmdArgsVersion is Just, it will display the version and exit.
In all other circumstances it will return a value.
Additionally, if cmdArgsVerbosity is Just (see verbosity) it will set the verbosity (see setVerbosity).

data CmdArgs a Source

A structure to store the additional data relating to --help, --version, --quiet and --verbose.

Constructors

CmdArgs

Fields

cmdArgsValue :: a: The underlying value being wrapped.
cmdArgsHelp :: Maybe String: Just if --help is given, then gives the help message for display, including a trailing newline.
cmdArgsVersion :: Maybe String: Just if --version is given, then gives the version message for display, including a trailing newline.
cmdArgsVerbosity :: Maybe Verbosity: Just if --quiet or --verbose is given, then gives the verbosity to use.
cmdArgsPrivate :: CmdArgsPrivate: Private: Only exported due to Haddock limitations.

Instances

Functor CmdArgs
Eq a => Eq (CmdArgs a)
Data a => Data (CmdArgs a)
Ord a => Ord (CmdArgs a)
Show a => Show (CmdArgs a)
Typeable (* -> *) CmdArgs

Constructing command lines

Attributes can work on a flag (inside a field), on a mode (outside the record), or on all modes (outside the modes call).

opt :: (Show a, Typeable a) => a -> Ann Source

Flag: "I want users to be able to omit the value associated with this flag."

Make the value of a flag optional. If --flag is given, it will be treated as --flag=this_argument.

{hello = def &= opt "foo"}
  -h --hello[=VALUE]    (default=foo)

Note that all flags in CmdArgs are optional, and if omitted will use their default value. Those annotated with opt also allow the flag to be present without an associated value. As an example:

{hello = "DEFAULT" &= opt "OPTIONAL"}

$ main
{hello = "DEFAULT"}
$ main --hello
{hello = "OPTIONAL"}
$ main --hello=VALUE
{hello = "VALUE"}

typ :: String -> Ann Source

Flag: "For this flag, users need to give something of type ..."

The the type of a flag's value, usually upper case. Only used for the help message. Commonly the type will be FILE (typFile) or DIR (typDir).

{hello = def &= typ "MESSAGE"}
  -h --hello=MESSAGE

typFile :: Ann Source

Flag: "Users must give a file for this flag's value."

Alias for typ FILE.

typDir :: Ann Source

Flag: "Users must give a directory for this flag's value."

Alias for typ DIR.

help :: String -> Ann Source

Flag/Mode: "The help message is ..."

Descriptive text used in the help output.

{hello = def &= help "Help message"}
  -h --hello=VALUE      Help message

name :: String -> Ann Source

Flag: "Use this flag name for this field."

Add flags which trigger this option.

{hello = def &= name "foo"}
  -h --hello --foo=VALUE

args :: Ann Source

Flag: "Put non-flag arguments here."

All argument flags not captured by argPos are returned by args.

{hello = def &= args}

argPos :: Int -> Ann Source

Flag: "Put the nth non-flag argument here."

This field should be used to store a particular argument position (0-based).

{hello = def &= argPos 0}

groupname :: String -> Ann Source

Flag/Mode: "Give these flags/modes a group name in the help output."

This mode will be used for all following modes/flags, until the next groupname.

{hello = def &= groupname "Welcomes"}
Welcomes
  -h --hello=VALUE

details :: [String] -> Ann Source

Mode: "A longer description of this mode is ..."

Suffix to be added to the help message.

Sample{..} &= details ["More details on the website www.example.org"]

summary :: String -> Ann Source

Modes: "My program name/version/copyright is ..."

One line summary of the entire program, the first line of --help and the only line of --version. If the string contains a version number component will also provide --numeric-version.

Sample{..} &= summary "CmdArgs v0.0, (C) Neil Mitchell 1981"

auto :: Ann Source

Mode: "If the user doesn't give a mode, use this one."

This mode is the default. If no mode is specified and a mode has this attribute then that mode is selected, otherwise an error is raised.

modes [Mode1{..}, Mode2{..} &= auto, Mode3{..}]

program :: String -> Ann Source

Modes: "My program executable is named ..."

This is the name of the program executable. Only used in the help message. Defaults to the type of the mode.

Sample{..} &= program "sample"

explicit :: Ann Source

Flag: "Don't guess any names for this field."

A field should not have any flag names guessed for it. All flag names must be specified by flag.

{hello = def &= explicit &= name "foo"}
  --foo=VALUE

ignore :: Ann Source

Flag/Mode: "Ignore this field, don't let the user set it."

A mode or field is not dealt with by CmdArgs.

{hello = def, extra = def &= ignore}
  --hello=VALUE

verbosity :: Ann Source

Modes: "My program needs verbosity flags."

Add --verbose and --quiet flags.

helpArg :: [Ann] -> Ann Source

Modes: "Customise the help argument."

Add extra options to a help argument, such as help, name, ignore or explicit.

Sample{..} &= helpArg [explicit, name "h"]

versionArg :: [Ann] -> Ann Source

Modes: "Customise the version argument."

Add extra options to a version argument, such as help, name, ignore, summary or explicit.

Sample{..} &= versionArg [ignore]

verbosityArgs :: [Ann] -> [Ann] -> Ann Source

Modes: "Customise the verbosity arguments."

Add extra options to a verbosity arguments (--verbose and --quiet), such as help, name, ignore or explicit. The verbose options come first, followed by the quiet options.

Sample{..} &= verbosityArgs [ignore] [name "silent", explicit]

noAtExpand :: Ann Source

Program: "Turn off @ expansion."

Usually arguments starting with @ are treated as a file containing a set of arguments. This annotation turns off that behaviour.

Sample{..} &= noAtExpand

Impure

(&=) :: Data val => val -> Ann -> val Source

Add an annotation to a value. Note that if the value is evaluated more than once the annotation will only be available the first time.

modes :: Data val => [val] -> val Source

Modes: "I want a program with multiple modes, like darcs or cabal."

Takes a list of modes, and creates a mode which includes them all. If you want one of the modes to be chosen by default, see auto.

data Modes = Mode1 | Mode2 | Mode3 deriving Data
cmdArgs $ modes [Mode1,Mode2,Mode3]

enum :: Data val => [val] -> val Source

Flag: "I want several different flags to set this one field to different values."

This annotation takes a type which is an enumeration, and provides multiple separate flags to set the field to each value. The first element in the list is used as the value of the field.

data State = On | Off deriving Data
data Mode = Mode {state :: State}
cmdArgs $ Mode {state = enum [On &= help "Turn on",Off &= help "Turn off"]}
  --on   Turn on
  --off  Turn off

This annotation can be used to allow multiple flags within a field:

data Mode = Mode {state :: [State]}
cmdArgs $ Mode {state = enum [[] &= ignore, [On] &= help "Turn on", [Off] &= help "Turn off"]}

Now --on --off would produce Mode [On,Off].

Pure

(+=) :: Annotate ann -> ann -> Annotate ann infixl 2 Source

Add an annotation to a value.

record :: Data a => a -> [Annotate ann] -> Annotate ann Source

Create a constructor/record. The first argument should be the type of field, the second should be a list of fields constructed originally defined by := or :=+.

This operation is not type safe, and may raise an exception at runtime if any field has the wrong type or label.

atom :: Data val => val -> Annotate ann Source

Lift a pure value to an annotation.

data Annotate ann Source

This type represents an annotated value. The type of the underlying value is not specified.

Constructors

forall c f . (Data c, Data f) => (c -> f) := f infix 3

Construct a field, fieldname := value.

Instances

Typeable (* -> *) Annotate

enum_ :: (Data c, Data f) => (c -> f) -> [Annotate Ann] -> Annotate Ann Source

Like enum, but using the pure annotations.

modes_ :: [Annotate Ann] -> Annotate Ann Source

Like modes, but using the pure annotations.

Re-exported for convenience

Provides a few opaque types (for writing type signatures), verbosity control, default values with def and the Data/Typeable type classes.

module System.Console.CmdArgs.Verbosity

module System.Console.CmdArgs.Default

data Ann Source

The general type of annotations that can be associated with a value.

Instances

Eq Ann
Data Ann
Ord Ann
Show Ann
Typeable * Ann

data Mode a Source

A mode. Do not use the Mode constructor directly, instead use mode to construct the Mode and then record updates. Each mode has three main features:

A list of submodes (modeGroupModes)
A list of flags (modeGroupFlags)
Optionally an unnamed argument (modeArgs)

To produce the help information for a mode, either use helpText or show.

Instances

Remap Mode
Show (Mode a)

class Typeable * a => Data a

The Data class comprehends a fundamental primitive gfoldl for folding over constructor applications, say terms. This primitive can be instantiated in several ways to map over the immediate subterms of a term; see the gmap combinators later in this class. Indeed, a generic programmer does not necessarily need to use the ingenious gfoldl primitive but rather the intuitive gmap combinators. The gfoldl primitive is completed by means to query top-level constructors, to turn constructor representations into proper terms, and to list all possible datatype constructors. This completion allows us to serve generic programming scenarios like read, show, equality, term generation.

The combinators gmapT, gmapQ, gmapM, etc are all provided with default definitions in terms of gfoldl, leaving open the opportunity to provide datatype-specific definitions. (The inclusion of the gmap combinators as members of class Data allows the programmer or the compiler to derive specialised, and maybe more efficient code per datatype. Note: gfoldl is more higher-order than the gmap combinators. This is subject to ongoing benchmarking experiments. It might turn out that the gmap combinators will be moved out of the class Data.)

Conceptually, the definition of the gmap combinators in terms of the primitive gfoldl requires the identification of the gfoldl function arguments. Technically, we also need to identify the type constructor c for the construction of the result type from the folded term type.

In the definition of gmapQx combinators, we use phantom type constructors for the c in the type of gfoldl because the result type of a query does not involve the (polymorphic) type of the term argument. In the definition of gmapQl we simply use the plain constant type constructor because gfoldl is left-associative anyway and so it is readily suited to fold a left-associative binary operation over the immediate subterms. In the definition of gmapQr, extra effort is needed. We use a higher-order accumulation trick to mediate between left-associative constructor application vs. right-associative binary operation (e.g., (:)). When the query is meant to compute a value of type r, then the result type withing generic folding is r -> r. So the result of folding is a function to which we finally pass the right unit.

With the -XDeriveDataTypeable option, GHC can generate instances of the Data class automatically. For example, given the declaration

data T a b = C1 a b | C2 deriving (Typeable, Data)

GHC will generate an instance that is equivalent to

instance (Data a, Data b) => Data (T a b) where
    gfoldl k z (C1 a b) = z C1 `k` a `k` b
    gfoldl k z C2       = z C2

    gunfold k z c = case constrIndex c of
                        1 -> k (k (z C1))
                        2 -> z C2

    toConstr (C1 _ _) = con_C1
    toConstr C2       = con_C2

    dataTypeOf _ = ty_T

con_C1 = mkConstr ty_T "C1" [] Prefix
con_C2 = mkConstr ty_T "C2" [] Prefix
ty_T   = mkDataType "Module.T" [con_C1, con_C2]

This is suitable for datatypes that are exported transparently.

Minimal complete definition

gunfold, toConstr, dataTypeOf

Instances

Data Bool
Data Char
Data Double
Data Float
Data Int
Data Int8
Data Int16
Data Int32
Data Int64
Data Integer
Data Ordering
Data Word
Data Word8
Data Word16
Data Word32
Data Word64
Data Exp
Data Match
Data Clause
Data Pat
Data Type
Data Dec
Data Name
Data FunDep
Data Pred
Data TyVarBndr
Data ()
Data Version
Data ModName
Data PkgName
Data Module
Data OccName
Data NameFlavour	Although the NameFlavour type is abstract, the Data instance is not. The reason for this is that currently we use Data to serialize values in annotations, and in order for that to work for Template Haskell names introduced via the 'x syntax we need gunfold on NameFlavour to work. Bleh! The long term solution to this is to use the binary package for annotation serialization and then remove this instance. However, to do _that_ we need to wait on binary to become stable, since boot libraries cannot be upgraded separately from GHC itself. This instance cannot be derived automatically due to bug #2701
Data NameSpace
Data Info
Data ModuleInfo
Data Fixity
Data FixityDirection
Data Lit
Data Body
Data Guard
Data Stmt
Data Range
Data TySynEqn
Data FamFlavour
Data Foreign
Data Callconv
Data Safety
Data Pragma
Data Inline
Data RuleMatch
Data Phases
Data RuleBndr
Data AnnTarget
Data Strict
Data Con
Data TyLit
Data Role
Data AnnLookup
Data Ann
Data Verbosity
Data a => Data [a]
(Data a, Integral a) => Data (Ratio a)
(Data a, Typeable * a) => Data (Ptr a)
(Data a, Typeable * a) => Data (ForeignPtr a)
Data a => Data (Maybe a)
Data a => Data (CmdArgs a)
(Data a, Data b) => Data (Either a b)
(Data a, Data b) => Data (a, b)
(Typeable * a, Data a, Data b, Ix a) => Data (Array a b)
Data t => Data (Proxy * t)
(Data a, Data b, Data c) => Data (a, b, c)
(Coercible * a b, Data a, Data b) => Data (Coercion * a b)
((~) * a b, Data a) => Data ((:~:) * a b)
(Data a, Data b, Data c, Data d) => Data (a, b, c, d)
(Data a, Data b, Data c, Data d, Data e) => Data (a, b, c, d, e)
(Data a, Data b, Data c, Data d, Data e, Data f) => Data (a, b, c, d, e, f)
(Data a, Data b, Data c, Data d, Data e, Data f, Data g) => Data (a, b, c, d, e, f, g)

class Typeable a

The class Typeable allows a concrete representation of a type to be calculated.

Minimal complete definition

typeRep#

Instances

Typeable * Bool
Typeable * Char
Typeable * Double
Typeable * Float
Typeable * Int
Typeable * Int8
Typeable * Int16
Typeable * Int32
Typeable * Int64
Typeable * Integer
Typeable * Ordering
Typeable * RealWorld
Typeable * Word
Typeable * Word8
Typeable * Word16
Typeable * Word32
Typeable * Word64
Typeable * Exp
Typeable * Match
Typeable * Clause
Typeable * Pat
Typeable * Type
Typeable * Dec
Typeable * Name
Typeable * FunDep
Typeable * Pred
Typeable * TyVarBndr
Typeable * ()
Typeable * Handle
Typeable * Handle__
Typeable * Version
Typeable * PatternMatchFail
Typeable * RecSelError
Typeable * RecConError
Typeable * RecUpdError
Typeable * NoMethodError
Typeable * NonTermination
Typeable * NestedAtomically
Typeable * BlockedIndefinitelyOnMVar
Typeable * BlockedIndefinitelyOnSTM
Typeable * Deadlock
Typeable * AssertionFailed
Typeable * SomeAsyncException
Typeable * AsyncException
Typeable * ArrayException
Typeable * ExitCode
Typeable * IOException
Typeable * ErrorCall
Typeable * ArithException
Typeable * TypeRep
Typeable * TyCon
Typeable * SomeException
Typeable * ModName
Typeable * PkgName
Typeable * Module
Typeable * OccName
Typeable * NameFlavour
Typeable * NameSpace
Typeable * Info
Typeable * ModuleInfo
Typeable * Fixity
Typeable * FixityDirection
Typeable * Lit
Typeable * Body
Typeable * Guard
Typeable * Stmt
Typeable * Range
Typeable * TySynEqn
Typeable * FamFlavour
Typeable * Foreign
Typeable * Callconv
Typeable * Safety
Typeable * Pragma
Typeable * Inline
Typeable * RuleMatch
Typeable * Phases
Typeable * RuleBndr
Typeable * AnnTarget
Typeable * Strict
Typeable * Con
Typeable * TyLit
Typeable * Role
Typeable * AnnLookup
Typeable * Ann
Typeable * Verbosity
(Typeable (k1 -> k) s, Typeable k1 a) => Typeable k (s a)	Kind-polymorphic Typeable instance for type application
Typeable ((* -> *) -> Constraint) Alternative
Typeable ((* -> *) -> Constraint) Applicative
Typeable (* -> * -> * -> * -> * -> * -> * -> *) (,,,,,,)
Typeable (* -> * -> * -> * -> * -> * -> *) (,,,,,)
Typeable (* -> * -> * -> * -> * -> *) (,,,,)
Typeable (* -> * -> * -> * -> *) (,,,)
Typeable (* -> * -> * -> *) (,,)
Typeable (* -> * -> * -> *) STArray
Typeable (* -> * -> *) (->)
Typeable (* -> * -> *) Either
Typeable (* -> * -> *) (,)
Typeable (* -> * -> *) ST
Typeable (* -> * -> *) Array
Typeable (* -> * -> *) STRef
Typeable (* -> *) []
Typeable (* -> *) Ratio
Typeable (* -> *) IO
Typeable (* -> *) Ptr
Typeable (* -> *) FunPtr
Typeable (* -> *) ForeignPtr
Typeable (* -> *) IORef
Typeable (* -> *) Maybe
Typeable (* -> *) CmdArgs
Typeable (* -> *) Annotate
Typeable (* -> Constraint) Monoid
Typeable (k -> *) (Proxy k)
Typeable (k -> k -> *) (Coercion k)
Typeable (k -> k -> *) ((:~:) k)