Oh, good point! Yes, that sounds like it should work well, sorry I didn't think of it.<div> </div><div>Robby On Wednesday, November 21, 2012, Tobias Hammer wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> On Wed, 21 Nov 2012 15:33:06 +0100, Greg Hendershott <<a>greghendershott@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> The lexical context you're picking up to put on #'args in the lam macro is the context that's sitting on the parentheses in the first argument to 'lam' in the body of 'expand-to-lam'. that context has no "x" bound. </blockquote> OK, that explains why x is not bound. Thanks! <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> This is the trouble with these kinds of macros: you have to be careful to propagate the correct lexical information thru. In this case, you can either change expand-to-lam to carry its argument's lexical context onto that open paren there or you can change lam to use a different spot to get its lexical information (one that's already being carried thru, eg the context on the actual variables for example). </blockquote> I want lam to be usable by other macros without the latter needing to cooperate explicitly; I want them to "just work". So I prefer the second way. </blockquote> As Robby explained you are using the context of the list of args for all arguments, which is in this case a wrong one. One context that should be valid in all cases in your example is the one of the arguments itself. If you unpack the arguments, do whatever you want to them and then reapply the context you stripped before, it should (as far as i understand) work: (define-syntax (lam stx) (syntax-case stx () [(_ args body ...) (with-syntax ([conv-args (for/list ([a (syntax->list #'args)]) (define a-datum (syntax->datum a)) ;; do whatever you want with a-datum (datum->syntax a a-datum))]) #`(lambda conv-args body ...))])) Other macros only have to cooperate in the 'normal' way, i.e. they have to make sure that the arguments they pass in have the right context. Tobias </blockquote></div>