On Sat, Jun 27, 2009 at 5:44 AM, Niklas Broberg
Hi all,
Following the discussion on the use of 'forall' and extensions that use it [1], I would hereby like to propose that the ExistentialQuantification extension is deprecated.
My rationale is as follows. With the introduction of GADTs, we now have two ways to write datatype declarations, the old simple way and the GADTs way. The GADTs way fits better syntactically with Haskell's other syntactic constructs, in all ways. The general style is (somewhat simplified) "keyword type 'where' decls", where keyword can in Haskell 98 be class or instance, but with GADTs also data. The old simple way of defining data types is the odd one out. It certainly has its uses though, in particular when defining some simple (but possibly large) enum-like datatype (like cabal's Extension type incidentally), then it obviously becomes tedious to have to restate the trivial type signature for each constructor.
How does the support of the extensions differ between existing implementations? Antoine