Type Functions in GHC

The main development repo of GHC now includes an extended version of the typed intermediate language, Core, that includes a notion of type equality coercions with the aim to support a whole range of source language features that make essential use of non-syntactic equality, such as GADTs, associated types, functional dependencies, and even general type functions.

Type functions

We previously introduced an extension of type classes with type-indexed data types, called associated data types, and type functions, called associated type synonyms. F_C enables us to generalise associated types to a general form of open type functions.

Documentation

Documentation is available from the GHC Developer Wiki:

• Type Functions: The precise source language extension adding type functions as well as the gory details of its implementation and the current implementation status.
• Intermediate Types: Details on the realisation of System F_C in the form of GHC's new Core language.

Getting the implementation

To grab the current implementations, do the following:

% darcs get --partial http://darcs.haskell.org/ghc/
% cd ghc
% chmod +x ./darcs-all
% ./darcs-all get

Then, follow the HACKING instructions.

People (alphabetically)

• Manuel Chakravarty, University of New South Wales
• Kevin Donnelly, Microsoft Research Cambridge & Boston University
• Simon Peyton Jones, Microsoft Research Cambridge
• Martin Sulzmann, National Univeristy of Singapore