-
chak@cse.unsw.edu.au. authored
This patch introduces type checking for type families of which associated type synonyms are a special case. E.g. type family Sum n m type instance Sum Zero n = n type instance Sum (Succ n) m = Succ (Sum n m) where data Zero -- empty type data Succ n -- empty type In addition we support equational constraints of the form: ty1 ~ ty2 (where ty1 and ty2 are arbitrary tau types) in any context where type class constraints are already allowed, e.g. data Equals a b where Equals :: a ~ b => Equals a b The above two syntactical extensions are disabled by default. Enable with the -XTypeFamilies flag. For further documentation about the patch, see: * the master plan http://hackage.haskell.org/trac/ghc/wiki/TypeFunctions * the user-level documentation http://haskell.org/haskellwiki/GHC/Indexed_types The patch is mostly backwards compatible, except f...
5822cb8d