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

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

Handle

type Exception = Throw #

Capability to throw an exception of type exn

Handlers

try #

Arguments

:: forall exn (es :: Effects) a. (forall (e :: Effects). Throw 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). Throw 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). Throw 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
=> Throw 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
-> Throw 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)