[plt-scheme] Keyword argument macros

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Tue Jan 6 08:43:15 EST 2009

At Tue, 6 Jan 2009 06:43:33 -0600, "Casey Klein" wrote:
> I'd like to write a macro that accepts keyword arguments, e.g.,
> (my-macro e1 #:kw e2 e3). syntax-case isn't much help in parsing the
> macro's input. Do I need to do this parsing myself, checking for
> duplicate/missing keywords, or is there some library solution I'm
> missing?

I don't think you're missing anything. 

I've implemented form using something like

  (syntax-case stx ()
    [(_ #:optional-stuff a expr ...)
     (generate #'(expr ...) #'a)]
    [(_ expr ...)
     (generate #'(expr ...) #f)])

which works ok (but not great) if the keyword addition has a fixed
position in the form and if there are not many optional parts. For more
complex forms, I've so far resorted to manual parsing.

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