Safe Haskell | Safe |
---|---|
Language | Haskell2010 |
Contains the core functionality for LambdaOptions.
Synopsis
- runOptions :: Options r () -> [String] -> Either OptionsError [r]
- data Options r a
- data OptionsError = ParseFailed {}
- type OptionCallback r f = (GetOpaqueParsers r f, Wrap r f)
- addOption :: forall r f. OptionCallback r f => Keyword -> f -> Options r ()
- getHelpDescription :: Options r () -> String
- getKeywords :: Options r () -> [Keyword]
Documentation
runOptions :: Options r () -> [String] -> Either OptionsError [r] Source #
Tries to parse the supplied options against input arguments.
If successful, parsed option callback results are returned in Right
. Otherwise
an OptionsError
is returned in Left
.
Example program:
import System.Environment import Text.LambdaOptions options :: Options (IO ()) () options = do addOption (kw ["--help", "-h"] `text` "Display this help text.") $ do putStrLn "Usage:" putStrLn $ getHelpDescription options addOption (kw "--user" `argText` "NAME" `text` "Prints name.") $ \name -> do putStrLn $ "Name:" ++ name addOption (kw "--user" `argText` "NAME AGE" `text` "Prints name and age.") $ \name age -> do putStrLn $ "Name:" ++ name ++ " Age:" ++ show (age :: Int) main :: IO () main = do args <- getArgs case runOptions options args of Left e -> do putStrLn $ parseFailedMessage e putStrLn $ getHelpDescription options Right actions -> sequence_ actions
>>>
example.exe --user HaskellCurry 81 --user GraceHopper
Name:HaskellCurry Age:81 Name:GraceHopper>>>
example.exe -h
Usage: -h, --help Display this help text. --user NAME Prints name. --user NAME AGE Prints name and age.>>>
example.exe --user Pythagoras LXXV
Unknown option at index 2: `LXXV' Usage: -h, --help Display this help text. --user NAME Prints name. --user NAME AGE Prints name and age.
A monad for parsing options.
data OptionsError Source #
Contains information about what went wrong during an unsuccessful options parse.
Instances
Show OptionsError Source # | |
Defined in Text.LambdaOptions.Core showsPrec :: Int -> OptionsError -> ShowS # show :: OptionsError -> String # showList :: [OptionsError] -> ShowS # |
type OptionCallback r f = (GetOpaqueParsers r f, Wrap r f) Source #
Describes the callback f
to be called for a successfully parsed option.
The function (or value) f
can have any arity and ultimately returns a value with type r
Each of the callback's arguments must have a type t
which implements Parseable
and Typeable
.
Think of this as the following constraint synonym:
type OptionCallback r f = (f ~ (Parseable t*, Typeable t*) => t0 -> t1 -> ... -> tN -> r)
Example callbacks:
f0 = putStrLn "Option parsed!" :: IO () f1 = put :: String -> State String () f2 = liftIO . print :: (MonadIO m) => Int -> m () f3 name year ratio = lift (print (name, year, ratio)) :: (MonadTrans m) => String -> Int -> Float -> m IO () f4 = 7 :: Int f5 = (:) :: Double -> [Double] -> [Double]
addOption :: forall r f. OptionCallback r f => Keyword -> f -> Options r () Source #
Adds the supplied option to the Options m a ()
context.
If the keyword is matched and the types of the callback's parameters can successfully be parsed, the callback is called with the parsed arguments.
getHelpDescription :: Options r () -> String Source #
Produces the help description given by the input options.