Here's one more solution, using "template metafunctions" (inspired by
Redex's metafunctions). And yes, most of the point of template
metafunctions is to have something that cooperates with ellipses like
you want.
> (require syntax/parse
syntax/parse/experimental/template
racket/syntax)
> (define-template-metafunction join
(syntax-parser
[(_ a:id b:id)
(format-id #'a "~a-~a" #'a #'b)]))
> (syntax-parse #'(foo a b c)
[(f:id s:id ...)
(template (list (join f s) ...))])
#<syntax::247 (list foo-a foo-b foo-c)>
Ryan
On 9/2/15 7:00 AM, Konrad Hinsen wrote:
Hi everyone,
I am working on what I consider a simple macro, but after reading all
of the macro-related documentation twice, I still don't see how to do
this.
I want to transform
(foo a b c)
to
(list foo-a foo-b foo-c)
Here is my best attempt (using syntax/parse):
(syntax-parse #'(foo a b c)
[(f:id s:id ...)
(list (format-id #'f "foo-~a" #'s) ...)])
This yields the error message
syntax: missing ellipsis with pattern variable in template
In fact, what I want is do something like map over the ellipsis pattern,
but I haven't seen any example for doing this.
Help, please!
Thanks in advance,
Konrad.
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