Re: [Chicken-users] stressing the new hygienic macros

[Alex Shinn]

Michele Simionato <address@hidden> writes:

> I have subscribed again the list after a few years of absence, because I 
> wanted
> to try the new and improved hygienic Chicken ;-)
> As first experiment, I tried to stress a bit syntax-rules. I tried the 
> following
> at the REPL:
>
>> (define-syntax very-static-table
>   (syntax-rules ()
>     ((_ (name value) ...)
>       (syntax-rules (<names> name ...)
>         ((_ <names>) '(name ...))
>         ((_ name) value) ...))))
>
>  > (define-syntax color
>   (very-static-table (red 0) (green 1) (blue 2)))
>
> Error: unbound variable: red

This is left unspecified by R5RS which says nothing about
transformer specs other than syntax-rules.  Chicken 4
extends define-syntax with the er-macro-transformer spec,
(and with raw lambdas which mean the same thing), but these
are hard-coded.

Al* Petrofsky specifically argued that this be allowed, as
well as

  (let-syntax ((foo some-other-macro))
    ...)

and implemented it in his alexpander.  It's a necessary
feature for the user to provide his/her own syntax
transformers defined in terms of existing transformers
(e.g. super-syntax-rules with extended pattern matching).

The other syntactic-closures and riaxpander macros systems
in Chicken 3 also support it, as do MIT Scheme, Ikarus and
Chibi-Scheme.  PLT doesn't.  A lot of interpreters do, but
more by coincidence than design, and the fact that they
represent macros as first-class values (which would make
separate compilation, even to bytecode, much harder).

-- 
Alex