Re: problems with syntax-case and with-syntax

[Chris Vine <vine35792468@gmail.com>]

On Sun, 27 Aug 2017 20:36:53 -0400
Mark H Weaver <mhw@netris.org> wrote:
> Matt Wette <matt.wette@gmail.com> writes:
> 
> > Q1) The code below creates two macros.  One called `define-foo'
> > which generates a new identifier and then defines that to #t.  The
> > other, `define-foo/p', generates the same identifier (lexical
> > issue?) and another identifier, then "calls" define-foo and then
> > uses both identifiers in a `define'.  When executed I get this
> > error:
> >
> > scheme@(guile-user)> (define-foo/p abc)
> > ;;; <stdin>:2:0: warning: possibly unbound variable `wrap-abc'
> > <unnamed port>:2:0: <unnamed port>:2:0: In procedure module-lookup:
> > Unbound variable: wrap-abc
> >
> > What am I doing wrong here?  
> 
> The problem is that in Guile 2.2, whenever (define <id> ...) is found
> in the expanded code, where <id> was introduced by a macro (i.e. not
> passed as an explicit argument to the macro), Guile will rewrite the
> <id> into a new name based on the hash of the entire definition form.
> 
> I don't know of any way to make this work without passing 'wrap-abc'
> explicitly as an argument to the 'define-foo' macro.
> 
> FWIW, I've always been opposed to these non-standard semantics, but
> they were included in Guile 2.2 over my strenuous objections:
> 
>   https://lists.gnu.org/archive/html/guile-devel/2014-01/msg00061.html
>   https://lists.gnu.org/archive/html/guile-devel/2011-11/msg00021.html
>   https://lists.gnu.org/archive/html/guile-devel/2011-11/msg00042.html

How interesting.

There seems very little uniformity in how the different schemes which I
happen to have available deal with the issue of top level hygiene with
nested macros.  Given the example in paragraph 6.10.10 of the guile-2.2
manual, after the definitions of both 'foo' and 'bar' have both been
made the following schemes evaluate '(foo)' as 37:

  guile-2.0, chicken;

and the following evaluate it as 42:

  guile-2.2, chez, kawa.

Chris