The control-monad-exception package

[ Tags: control, failure, library, mit, monads ] [ Propose Tags ]

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 his 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

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), control-monad-failure, extensible-exceptions (==0.1.*), monadloc, monads-fd (==0.0.*), mtl, pretty, transformers (>=0.0.1 && <0.2) [details]
License PublicDomain
Author Pepe Iborra
Maintainer pepeiborra@gmail.com
Category Control, Monads
Home page http://pepeiborra.github.com/control-monad-exception
Uploaded Mon Nov 2 22:08:09 UTC 2009 by PepeIborra
Distributions NixOS:0.11.2
Downloads 7817 total (45 in the last 30 days)
Rating 0.0 (0 ratings) [clear rating]
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Status Docs not available [build log]
All reported builds failed as of 2016-12-31 [all 7 reports]
Hackage Matrix CI

Modules

  • Control
    • Monad
      • Control.Monad.Exception
        • Control.Monad.Exception.Catch
        • Control.Monad.Exception.Throws

Flags

NameDescriptionDefaultType
transformers

Use transformers and monads-fd instead of mtl

EnabledAutomatic
extensibleexceptions

Use extensible-exception package

DisabledAutomatic

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

Downloads

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