Re: [Chicken-hackers] cond-expand and macros

[Kon Lovett]

On Nov 20, 2009, at 10:05 AM, Thomas Bushnell BSG wrote:

> On Thu, 2009-11-19 at 18:33 -0800, Kon Lovett wrote:
> > Features are converted to keywords. The colon suffix is just the
> > default read/print form; #:keyword is the context-independent form.
>
> The manual needs to document this; right now, one might have thought
> they were ordinary symbols given every example and description in the
> manual.

Please submit a bug report.

> > 'cond-expand' uses a function that ensures the tested symbol is a
> > keyword, so 'foo' & '#:foo' are legal.
> >
> > That the expansion-environment of a 'syntax-rules' transformer  
> > doesn't
> > recognize 'cond-expand' is a different problem. (Note that 'syntax-
> > rules' in Chicken 3 is not a core expander.)
>
> So the bug is more or less that the self-evaluating nature of keywords
> doesn't work in the meta-environment for macro expansion, I assume.

No, they are ordinary symbols (assuming the keyword read syntax is not  
present). The proffered symbol is converted to a keyword before  
comparison with the set of features. But this is performed by a  
procedure not the macro expander.

The self-evaluating nature of keywords works in macros AFAIK.

> (Certainly that it goes differently in Chicken3+syntax-case is no
> mystery, since the old syntax-case egg needed to provide its own
> implementation of cond-expand anyway.)
>
> Thomas

Best Wishes,
Kon