Automatically converting ASTs into compositional data types.
Template Haskell for converting an AST for a language written using normal algebraic data types into ones written using multi-sorted compositional data types (Data.Comp.Multi from the compdata library) so that you can use generic and modular operators on it. You might need to add additional constructors that can e.g.: convert a (Term e Foo) into a (Term e [Foo]).
The sCource files have comments showing example output for a simple language. See the examples directory for an extended example of generating a compositional data type for the entire Java language, with labelled variants as well as variants where an entire project of source files can be treated as a single AST -- and you can use the same operations on all of them!