| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
Network.Transport.Tests.Traced
Description
Add tracing to the IO monad (see examples).
- Usage
{-# LANGUAGE RebindableSyntax #-}
import Prelude hiding (catch, (>>=), (>>), return, fail)
import Traced- Example
test1 :: IO Int test1 = do Left x <- return (Left 1 :: Either Int Int) putStrLn "Hello world" Right y <- return (Left 2 :: Either Int Int) return (x + y)
outputs
Hello world *** Exception: user error (Pattern match failure in do expression at Traced.hs:187:3-9) Trace: 0 Left 2 1 Left 1
- Guards
Use the following idiom instead of using guard:
test2 :: IO Int test2 = do Left x <- return (Left 1 :: Either Int Int) True <- return (x == 3) return x
The advantage of this idiom is that it gives you line number information when the guard fails:
*Traced> test2 *** Exception: user error (Pattern match failure in do expression at Traced.hs:193:3-6) Trace: 0 Left 1
Synopsis
- class MonadS m where
- return :: MonadS m => a -> m a
- (>>=) :: (MonadS m, Traceable a) => m a -> (a -> m b) -> m b
- (>>) :: MonadS m => m a -> m b -> m b
- fail :: MonadS m => String -> m a
- ifThenElse :: Bool -> a -> a -> a
- data Showable = Show a => Showable a
- class Traceable a where
- traceShow :: Show a => a -> Maybe Showable
Documentation
Like Monad but bind is only defined for Traceable instances
ifThenElse :: Bool -> a -> a -> a Source #
Definition of ifThenElse for use with RebindableSyntax
class Traceable a where Source #