♦️ throwable-exceptions ♦️
throwable-exceptions gives an easy way to create the data types of Exception instance with TemplateHaskell,
and gives simple data types of Exception instance with its value constructor,
for your haskell project
-
throwable-exceptionsis available in
📚 Document is available in here 📚
💪 Why should we use this ? 💪
We want to throw some exception frequently, but the mostly throwable exceptions are not given by base.
throwable-exceptions complements it
Examples
- vvv The summary of the exact examples is available here vvv
You can create a data type of Exception instance by a line
{-# LANGUAGE TemplateHaskell #-}
module Main where
-- This is same as
--
-- data MyException a = MyException
-- { myExceptionCause :: String
-- , myExceptionClue :: a
-- } deriving (Show, Typeable)
-- instance (Typeable a, Show a) => Exception (MyException a)
--
declareException "MyException" ["MyException"]
-- This is same as
--
-- data TwoException a =
-- FirstException
-- { firstExceptionCause :: String
-- , firstExceptionClue :: a
-- } |
-- SecondException
-- { secondExceptionCause :: String
-- , secondExceptionClue :: a
-- } deriving (Typeable)
--
-- instance Show a => (TwoException a) where
-- ...
-- instance (Typeable a, Show a) => Exception (TwoException a)
--
declareException "TwoException" ["FirstException", "SecondException"]
main :: IO ()
main = do
print $ ([1..4] `at` 5 :: Either SomeException Int)
print $ MyException "hi" 10
print $ myException "poi"
print $ firstException "chino"
print $ secondException "cocoa"- the completely example
Several exceptions are defined by default
For example, IOException's value constructor is not given
But you can use Control.Exception.Throwable.IOException' instead
module Main where
main :: IO ()
main = do
throwM $ IOException' "oops!" "in main"
throwM $ ioException' "oops!"
👍
PR is welcome !
