Re: [Chicken-users] define-macro in Chicken 4.0

[Eduardo Cavazos]

On Fri, Mar 13, 2009 at 8:48 PM, Eduardo Cavazos 
<address@hidden> wrote:

> > Is there a way to define 'define-macro' in terms of the new explicit
> > renaming macros of Chicken 4.0? Or is it offered somewhere and I just missed
> > it?
> >
> > I know I know... 'define-macro' is bad. :-) But I have a bunch of code that
> > I'd like to have "just work" in Chicken 4.0 and worry about porting the
> > macros over later.

felix winkelmann wrote:

> It is possible to do that, but it will not work. The problem is that identifiers
> have to be renamed, depending on the syntactic environment they are
> used in (that's what all the hygiene is about). Macros introduce "alias"
> identifiers to prevent name-capture and if you write a macro which
> expands into the use of an identifier which was previously inserted by
> another macro expansion, you have to resolve the identifier properly
> to find the correct meaning. That is what the "rename" procedure in
> explicit renaming macros does. So macro-introduced identifiers will
> not be properly handled in your define-macro-style macros.
>
> The only way is to translate them to explicit-renaming, which is easier
> than it sounds, or use syntax-rules for the simple ones.

Well, I have some "portable" Scheme code; i.e. code that runs on a few 
implementations. In that code are some macros which intentionally break 
hygiene. So that rules out syntax-rules. Just about everybody supports 
define-macro so it was easy to achieve portability that way. 
Explicit-renaming macros don't seem to be as widely supported. For 
example, I don't think they're in Ypsilon or Ikarus. Didn't Clinger 
invent ER macros? They better damn well be in Larceny. ;-)

So... will syntax-case be offered as an egg?

syntax-case is much more widely supported (yeah I know, it's icky) and 
it allows responible bending of hygiene.

Ed