Hello all, I'm trying to reuse as much of the sweat and tear put into GHC as possible to derive a compiler for a language highly similar to Haskell in many aspects. The difference is that instead of constructing an expression of type IO (), the programmer has to provide a stream processor on the top level - whether this is an arrow structure or just a pure function mapping input to output is not decided yet. In other words, I want to allow the programmer to use full Haskell as a metaprogramming language to create an expression of a much more limited language. My idea was to move the relevant types into a module, and make my combinators simple data constructors behind the scene, so the Haskell phase would effectively build an AST. The tricky bit is that I don't necessarily want to make everything an explicit data constructor. For instance, I'd like to allow Haskell functions in the tree. Using the GHC API, I can get the Core representation of the metaprogram. What I'd like at this point is to evaluate the top level expression and still have a representation open to analysis (traversal, pretty printing, interpretation etc.), including lambdas; if this evaluation takes more time than some well-defined limit, I could treat it as a compile-time error. Basically, I want the constant that is the main program to be folded completely if possible during compile time, and signal an error in case it isn't or doesn't seem to be. The resulting structure would be transformed further by a separate application instead of the existing GHC backends. Unfortunately the GHC API is not very approachable for the uninitiated, so it's not clear to me whether this is even possible. Or is it simply such a bad idea that it's not even worth considering in the face of more conventional approaches? Gergely -- http://www.fastmail.fm - Same, same, but different...