At 2002-05-13 22:07, Ashley Yakeley wrote:

...

I've noticed something a bit unusual about Exception.catch.

Curiously, the definition of Exception.evaluate given in the GHC Libraries documentation sec. 5.12.3 is not that actually implemented by GHC.

evaluate' :: a -> IO a; evaluate' a = a `seq` return a;

"evaluate' undefined" is bottom, whereas "Expression.evaluate undefined" is an IO action that "fails" when executed. But both will be caught by Exception.catch.

This is bizarre: the definition of evaluate in Exception is exactly the one you gave above, yet they behave differently. You may have uncovered a compiler bug, I'll look into it. Cheers, Simon