Following recent discussions about instance declarations in Haskell-2
on the Haskell mailing list, and the suggestion that without
sufficient restrictions in this area Haskell's type system would
become undecidable, I decided to demonstrate this directly. In this
brief paper I present a
Hi all,
For some time now I have been wondering if it is possible to implement the
ST monad (with polymorphic newVar, writeVar, and readVar) in "pure"
Haskell. One might be allowed to use existential/universal quantification
in types, but no dynamic types or explicit type casts. I do not care
Is the following fragment legal Haskell? Section B.3 of the report is
not clear enough in this respect (at least for me :-}
foo x = do
case x of
_ - return '?'
If it *is* legal, GHC is wrong and Hugs is correct, otherwise GHC is
right and Hugs is too liberal and its library contains
