Unexcepted behaviour of Control.Exception.catch

[tobi@…]

Hi,

I'm running GHC Interactive, version 6.6, for Haskell 98 on a Suse Linux 9.3 Distribution.

the expression

Control.Exception.catch (Control.Exception.throw (Control.Exception.AssertionFailed? "error"))(\e -> return "caught")

evaluates to the expected value "caught". But the expression

Control.Exception.catch (return (Control.Exception.throw (Control.Exception.AssertionFailed? "error")))(\e -> return "caught")

stops with the message: "*** Exception: error which seems to be an error (at least from my point of view).

best regards

Tobias

[guest]

Hi,

I'm running GHC Interactive, version 6.6, for Haskell 98 on a Suse Linux 9.3 Distribution.

the expression

Control.Exception.catch (Control.Exception.throw (Control.Exception.AssertionFailed "error"))(\e -> return "caught")

evaluates to the expected value "caught". But the expression

Control.Exception.catch (return (Control.Exception.throw (Control.Exception.AssertionFailed "error")))(\e -> return "caught")

stops with the message: "*** Exception: error

which seems to be an error (at least from my point of view).

best regards

Tobias

[igloo]

This is actually expected behaviour. In the second expression the value throw ... isn't demanded by catch as it is happy with return <thunk>. The thunk is then evaluated outside of the catch and the exception is raised.