On 9/15/06, Robert Dockins <[EMAIL PROTECTED]> wrote:
You can define a direct fixed point combinator without relying on nominal recursion in Haskell, but it requires you to define a helper newtype.
That's really nifty! I'd been wondering whether you could do this too. Is there a reason for the extra `z' parameter?
Don't run this in GHC because it will diverge. Hugs works, however.
According to http://www.haskell.org/pipermail/glasgow-haskell-bugs/2001-August/001717.html this is due to a bug in the GHC inliner that probably won't be fixed. However, experimentation indicates you can work around the bug using the NOINLINE pragma: newtype Mu a = Roll { unroll :: Mu a -> a } fix :: (a -> a) -> a fix f = doink (Roll doink) where {-# NOINLINE doink #-} doink x = f ((unroll x) x) Mike _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
