Brandon S. Allbery KF8NH wrote:
On May 8, 2009, at 01:33 , Joe Fredette wrote:
That strikes me as being bad in a "I'm violating the Halting Problem" sort of way- but I'm not sure how. Is there some contradictory construction that could be built from such a function?
I don't think it is; surely the Haskell runtime knows which thunks it has evaluated. It just explicitly violates referential transparency, and therefore must be in IO. You may be thinking that it would return a result for _|_, but as described if you fed it _|_ it could only produce False (if the _|_ has been evaluated you would not be able to reach the test).
It could probably return True in GHC since you can catch exceptions. That still doesn't mean it solves the halting problem, of course. Ganesh =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================