Re: syntax-case guards

[Ian Price]

Aleix Conchillo Flaqué <address@hidden> writes:

> Hi,
>
> I'm trying to use a syntax-case guard when the pattern has ellipsis.
> So I have something like,
>
>       ((_ (struct (k v) ...))
>        (string? (syntax->datum #'k))
>        exp)
You were probably wanting this to apply to each and every k
individually? syntax-case does not work this way. Patterns with ellipsis
are expected to be matched with templates with ellipsis. Sorry.

> So, how do I make the guard when I have a pattern with ellipsis?
using every from (srfi srfi-1) or for-all from (rnrs lists) [same
procedure different name] you get

(every (compose string? syntax->datum) #'(k ...))

As an aside, this won't work in Racket, since they also make lists into
syntax objects, unlike psyntax or the r6rs.

-- 
Ian Price -- shift-reset.com

"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"