On Thu, Sep 27, 2007 at 04:59:49PM +0200, Wolfgang Jeltsch wrote: > Am Donnerstag, 27. September 2007 15:27 schrieb Roberto Zunino: > > Roberto Zunino wrote: > > > (Trac reports "database locked", posting here...) > > > > For those interested, here are the follow-ups: > > > > http://hackage.haskell.org/trac/ghc/ticket/1723 > > > > Regards, > > Zun. > > simonpj writes there: > > Manuel is about to nuke the old GADT stuff in favour of the new type-family > > stuff. > > This doesn’t mean that GADTs are being dropped in favor of type families, > does > it?
They are being dropped - from the typechecker. The old syntax will still work. data Foo a where A :: Foo Int B :: Foo Bool becomes data Foo a = (a ~ Int) => A | (a ~ Bool) => B (ignoring the H98 context issue). Then, in a case statement, traditional GADT refinement reduces to a special case of equality constraint discharging. (Simon, does this mean that non-~ discharging will become subject to GADT-style type annotation rules?) Stefan
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