-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 John Meacham wrote:
On Fri, Jul 06, 2007 at 11:26:00AM +0100, Neil Mitchell wrote:
ghci -fglasgow-exts Prelude> case (# 1 , 2 #) of (# a , b #) -> error $ show (a,b) *** Exception: (1,2)
You might expect there to be a prefix form of the unboxed tuple:
Prelude> case (#,#) 1 2 of (# a , b #) -> error $ show (a,b) <interactive>:1:7: parse error on input `,'
But there isn't. I've added special code into the Yhc code generator to deal with this particular constructor, so it no longer effects me.
Well, what would the type of (#,#) be? unboxed tuples can hold both boxed and unboxed values, so some sort of kind polymorphism would be needed to type the prefix form properly.
In GHC, some special functions have kind polymorphism http://hackage.haskell.org/trac/ghc/wiki/IntermediateTypes error :: forall a:?. String -> a (->) :: ?? -> ? -> * (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple) (and http://hackage.haskell.org/trac/ghc/changeset/2807 "But the 'real' type of error is: forall bv. forall a:Type bv. String -> a ") Or just saying it's illegal to partially apply (#,#) - which I believe is how (some of) GHC's primops work. Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGjj2rHgcxvIWYTTURAp03AJ4/kgTzuN6PHp5QFTOQBKJIKa8QtQCeLvjm hh9TO2NDFzZ2N+FYsgOORGU= =6GJm -----END PGP SIGNATURE-----