Safe Haskell	None
Language	Haskell2010

Bluefin.Exception

Contents

Handle
Handlers
Effectful operations

Description

This is an old interface and will be deprecated in the future. You are encouraged to use Bluefin.Capability.Throw instead.

Synopsis

data Exception exn (e :: Effects)
try :: forall exn (es :: Effects) a. (forall (e :: Effects). Exception exn e -> Eff (e :& es) a) -> Eff es (Either exn a)
handle :: forall exn (es :: Effects) a. (exn -> Eff es a) -> (forall (e :: Effects). Exception exn e -> Eff (e :& es) a) -> Eff es a
catch :: forall exn (es :: Effects) a. (forall (e :: Effects). Exception exn e -> Eff (e :& es) a) -> (exn -> Eff es a) -> Eff es a
throw :: forall (e :: Effects) (es :: Effects) ex a. e <: es => Exception ex e -> ex -> Eff es a
rethrowIO :: forall ex (es :: Effects) (e1 :: Effects) (e2 :: Effects) r. (e1 <: es, e2 <: es, Exception ex) => IOE e1 -> Exception ex e2 -> Eff es r -> Eff es r

Handle

data Exception exn (e :: Effects) #

Capability to throw an exception of type exn

Instances

Instances details

e <: es => OneWayCoercible (Exception ex e :: Type) (Exception ex es :: Type)
Instance details Defined in Bluefin.Internal Methods oneWayCoercibleImpl :: OneWayCoercibleD (Exception ex e) (Exception ex es) #
Handle (Exception exn)
Instance details Defined in Bluefin.Internal Methods handleImpl :: HandleD (Exception exn) #
CloneableHandle (Exception a)
Instance details Defined in Bluefin.Internal.CloneableHandle Methods cloneableHandleImpl :: CloneableHandleD (Exception a) #
e <: es => MonadFail (EffReader (Exception String e) es)
Instance details Defined in Bluefin.Internal Methods fail :: String -> EffReader (Exception String e) es a #

Handlers

try #

Arguments

:: forall exn (es :: Effects) a. (forall (e :: Effects). Exception exn e -> Eff (e :& es) a)
-> Eff es (Either exn a)	`Left` if the exception was thrown, `Right` otherwise

>>> runPureEff $ try $ \e -> do
      throw e 42
      pure "No exception thrown"
Left 42

handle #

Arguments

:: forall exn (es :: Effects) a. (exn -> Eff es a)	If the exception is thrown, apply this handler
-> (forall (e :: Effects). Exception exn e -> Eff (e :& es) a)
-> Eff es a

>>> runPureEff $ handle (pure . show) $ \e -> do
      throw e 42
      pure "No exception thrown"
"42"

catch #

Arguments

:: forall exn (es :: Effects) a. (forall (e :: Effects). Exception exn e -> Eff (e :& es) a)
-> (exn -> Eff es a)	If the exception is thrown, apply this handler
-> Eff es a

handle, but with the argument order swapped

Effectful operations

throw #

Arguments

:: forall (e :: Effects) (es :: Effects) ex a. e <: es
=> Exception ex e
-> ex	Value to throw
-> Eff es a

>>> runPureEff $ try $ \e -> do
      throw e 42
      pure "No exception thrown"
Left 42

>>> runPureEff $ try $ \e -> do
      pure "No exception thrown"
Right "No exception thrown"

rethrowIO #

Arguments

:: forall ex (es :: Effects) (e1 :: Effects) (e2 :: Effects) r. (e1 <: es, e2 <: es, Exception ex)
=> IOE e1
-> Exception ex e2
-> Eff es r
-> Eff es r	͘

Rethrow an exception raised by an IO action as a Bluefin exception.

runEff $ \io -> do
  r <- try $ \ex -> do
    rethrowIO @IOException io ex $ do
      effIO io (readFile "/tmp/doesnt-exist")

  effIO io $ putStrLn $ case r of
    Left e -> "Caught IOException:\n" ++ show e
    Right contents -> contents

Caught IOException:
/tmp/doesnt-exist: openFile: does not exist (No such file or directory)