Safe Haskell	Safe-Inferred
Language	Haskell2010

Bluefin.Exception

Contents

Handle
Handlers
Effectful operations

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) #

Handle to an exception of type exn

Instances

Instances details

Handle (Exception s)
Instance details Defined in Bluefin.Internal Methods mapHandle :: forall (e :: Effects) (es :: Effects). e :> es => Exception s e -> Exception s es #
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

handle, but with the argument order swapped

>>> 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

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)