So, I am writing a Scheme to JavaScript compiler. Because I want to write the macro and module system later, my idea was to use PLT Scheme's macro and module system, for now. Of course, this probably must be done with some kind of hack. I'm just trying to find one that is reliable. My first approach was to expand the module in the reader, store this expanded code (later will be translated to JavaScript), and replace the expressions in the expanded code by (void), so that the module just read, and to be returned by the reader, has no expressions. This is necessary because this code is to be evaluated later in the web browser. I'm using PLT to read, macro-expand but not evaluate the module. After reading what you wrote, I changed the process a bit. I still expand the code in the reader but then I return the read module, without replacing the expressions, but in a different language. In that new language, I have #%app to expand to #'(void). It works, but I have two languages that are different only in the provided #%app. Now I'm trying a new approach. Instead of expanding the module in the reader, I export a #%module-begin that replaces its subforms by a new macro that code-walks by using local-expand and some other hacks. This does not mix read and macro expansion levels, but I have to 10 times more code. Anyway, I know that all this is an hack, but... what is the best way to do what I want? Is there a less hacky way to proceed? On Fri, Nov 20, 2009 at 5:15 AM, Eli Barzilay <<a href="mailto:eli@barzilay.org">eli@barzilay.org</a>> wrote: <div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> But my first thought when I saw that (or rather when someone pointed at your question when you raised it on #scheme) is that you're trying to do some CL-ish kind of a code walker. (And I did see that you mentioned that this is a translation of CL code, so it seems relevant.) In this case, I think that trying to *match* on `#%app's is missing its point. The role of `#%app' is as a kind of a hook that you can use to redefine what happens on every point where a function is being applied *instead* of using a code walker. </blockquote></div> This code is not ported from CL. Although I do have some work in CL that I want to port to Scheme, this is just my experiments in a new system. I still don't known PLT (and Scheme) well enough to not make some newbie mistakes. That said, I've been writing CL for the last 3 years; probably I'm still thinking in CL. Thanks. Marco P.S. Yes, I am aware of Moby.