pattern matching

[Levent Erkok]

   HUGS> let ~(1,x) = (2,3) in x
   3

   GHCI> let ~(1,x) = (2,3) in x
   *** Exception: <no file>:0: Irrefutable pattern failed for pattern (1, x)

I think ghc is doing the right thing: the match should fail. Using the translation
of let into case as described in the report (section 3.12), one gets:

   case (2, 3) of ~(~(1,x)) -> x
  
This expression should cause a pattern matching failure. But hugs evaluates it to 3.
Interestingly:

   HUGS> case (2, 3) of ~(1,x) -> x
   Program error: {v1309 (2,Num_fromInt instNum_v29 3)}
 
which is the correct behavior. Shouldn't multiple tilde's be the same as just one?

(Hugs version: out of the CVS repository.)

-Levent.