The control-monad-exception package

[Tags:library, mit]

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

This package provides, among other things:

       f () = $withLocTH $ throw MyException
       g a  = $withLocTH $ f a

       main = runEMT $ $withLocTH $ do
       g () `catchWithSrcLoc` \loc (e::MyException) -> lift(putStrLn$ showExceptionWithTrace loc e)
        -- Running main produces the output:
       *Main> main
       MyException
        in Main(example.hs): (12,6)
           Main(example.hs): (11,7)

Properties

Versions 0.1, 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, 0.11.2
Dependencies base (>=3.0 && <5), extensible-exceptions (==0.1.*), monads-fd (==0.0.*), mtl, pretty, template-haskell, transformers (>=0.0.1 && <0.2) [details]
License PublicDomain
Author Pepe Iborra
Maintainer pepeiborra@gmail.com
Stability experimental
Category Control, Monads
Home page http://pepeiborra.github.com/control-monad-exception
Uploaded Tue Oct 27 18:35:36 UTC 2009 by PepeIborra
Distributions NixOS:0.11.2
Downloads 6653 total (106 in the last 30 days)
Votes
0 []
Status Docs uploaded by user
Build status unknown [no reports yet]

Modules

[Index]

Flags

NameDescriptionDefaultType
transformersUse transformers and monads-fd instead of mtlEnabledAutomatic
extensibleexceptionsUse extensible-exception packageDisabledAutomatic

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

Maintainer's Corner

For package maintainers and hackage trustees