At Tue, 12 Oct 2010 10:43:03 -0400, Eli Barzilay wrote: > An hour ago, Matthew Flatt wrote: > > At Mon, 11 Oct 2010 20:38:58 -0400, Eli Barzilay wrote: > > > > At Mon, 11 Oct 2010 19:15:09 -0400, Eli Barzilay wrote: > > > > > I'd love to see an implicit `#%begin', which could have the > > > > > above apply in more places automatically. (It was one of the > > > > > feature requests I asked for in the summer meeting.) > > > > > > > > Recall that no one solved the technical problem with where to > > > > pull the lexical context for the implicit `#%begin' or `#%body': > > > > > > > > http://lists.racket-lang.org/dev/archive/2010-July/003624.html > > > > > > I remember being confused with how that problem would look like, > > > but I don't think that I've seen an example where this would be > > > problematic. (I think that we talked about it, but I can't > > > remember any concrete details...) > > > > Can you say more about how the `squawk' example in the referenced > > post doesn't illustrate the problem? > > It doesn't specify any clear problem -- either that or I'm missing > something obvious... AFAICT, the problem that is described there is > similar to: > > (define-syntax-rule (squawk body ...) > (begin > (printf "squick ~a!" "squawk") > (let () body ...))) > > having the implicit `#%app' come from this macro's module rather than > the use site, for example, if it's defined in a module that has > implicitlty curried applications then the `printf' call becomes > curried.
Isn't the point of a configurable "implicit begin" that `squawk' can inherit the implicit-begin behavior of the use site instead of the definition site? That is, the intent of the example is that the `squawk' syntactic form has a body, and "body" means whatever it's configured to mean at the use site. Other macros, meanwhile, may expand to uses of `let' where the body of the `let' is meant to be used as in the context of the definition site (probably because the body of that `let' is not supplied as an argument to the macro). So, how does a macro implementor make the distinction between those kinds of `let's? _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
