The control-monad-exception package

[Tags: library, public-domain]

This package provides explicitly typed, checked exceptions as a library.

Computations throwing different types of exception can be combined seamlessly.

Example

 data Expr = Add Expr Expr | Div Expr Expr | Val Double
 eval (Val x)     = return x
 eval (Add a1 a2) = do
    v1 <- eval a1
    v2 <- eval a2
    let sum = v1 + v2
    if sum < v1 || sum < v2 then throw SumOverflow else return sum
 eval (Div a1 a2) = do
    v1 <- eval a1
    v2 <- eval a2
    if v2 == 0 then throw DivideByZero else return (v1 / v2)
 data DivideByZero = DivideByZero deriving (Show, Typeable)
 data SumOverflow  = SumOverflow  deriving (Show, Typeable)
 instance Exception DivideByZero
 instance Exception SumOverflow

GHCi infers the following types

 eval :: (Throws DivideByZero l, Throws SumOverflow l) => Expr -> EM l Double
 eval `catch` \ (e::DivideByZero) -> return (-1)  :: Throws SumOverflow l => Expr -> EM l Double
 runEM(eval `catch` \ (e::SomeException) -> return (-1))  :: Expr -> Double

In addition to explicitly typed exceptions this package provides:

 f () = do throw MyException
 g a  = do f a

 main = runEMT $ do g () `catchWithSrcLoc`
                        \loc (e::MyException) -> lift(putStrLn$ showExceptionWithTrace loc e)

 -- Running main produces the output:

 *Main> main
  MyException
    in f, Main(example.hs): (1,6)
       g, Main(example.hs): (2,6)
       main, Main(example.hs): (5,9)
       main, Main(example.hs): (4,16)

Properties

Versions0.1, 0.1.1, 0.1.2, 0.2, 0.3, 0.3.1, 0.3.2, 0.4, 0.4.1, 0.4.2, 0.4.3, 0.4.4, 0.4.5, 0.4.6, 0.4.7, 0.4.8, 0.5, 0.6, 0.8.0, 0.8.0.1, 0.8.0.2, 0.8.0.3, 0.8.0.4, 0.9.0, 0.9.1, 0.10.0, 0.10.1, 0.10.2, 0.10.3, 0.10.3.1, 0.11.1
Dependenciesbase (>=3.0 && <4), extensible-exceptions (==0.1.*), failure (>=0.1 && <0.3), lifted-base (>=0.2.1), monad-control (>=0.3), monadloc (>=0.7), transformers (>=0.2), transformers-base (>=0.4.1) or
base (==4.*), failure (>=0.1 && <0.3), lifted-base (>=0.2.1), monad-control (>=0.3), monadloc (>=0.7), transformers (>=0.2), transformers-base (>=0.4.1)
LicensePublicDomain
AuthorPepe Iborra
Maintainerpepeiborra@gmail.com
Stabilityprovisional
CategoryControl, Monads, Failure
Home pagehttp://pepeiborra.github.com/control-monad-exception
Bug trackerhttp://github.com/pepeiborra/control-monad-exception/issues
Source repositoryhead: git clone git://github.com/pepeiborra/control-monad-exception.git
Upload dateMon Apr 21 09:17:01 UTC 2014
Uploaded byPepeIborra
Downloads2660 total (220 in last 30 days)

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