Re: Looping local binding

[Keith Wright]

> From: Dmitry Dzhus <address@hidden>
> 
> That's terrific, Marco, and that code is almost clear to me.
> 
> I'm now strongly convinced that I should introduce myself to Scheme
> macro forms closer. What may a recommended definite guide to it? (I
> read SICP, but that book concentrates on other kind of things).

There is no definitive guide.  Macros in Scheme are
one of the more interesting areas of active research.
I do not think there are two implementations that
do it exactly the same way.  The sixth revised report,
which was ratified just weeks ago, has a macro system
that is nothing like that in Guile.

I learned a lot about it by reading the reference
implementation by Andre van Tonder,  Here is a
chunk from my email file.

        Good Luck in your search!

If you only want to know about Guile macros, I'm
afraid you have no choice but to read Guile documentation.

 -- Keith

> From: AndrevanTonder <address@hidden>
> Cc: address@hidden
> 
> > AndrevanTonder wrote:
> >>
> >>      R6RS Libraries and Syntax-case
> >>
> >> implementation is available at:
> >>
> >>     http://www.het.brown.edu/people/andre/macros
> >
> > This is a different library than what Abdulaziz Ghuloum announced recently,
> > <http://www.cs.indiana.edu/~aghuloum/r6rs-libraries/>?
> >
> > What are the differences?
> 
> As you noticed, there are currently two portable reference implementations
> of R6RS libraries and syntax-case.  Even though they are both R6RS compliant,
> there are indeed differences between them.  Aziz may have further comments,
> but the differences that are known to me are the following:
> 
>   * The largest difference is in how identifier import levels are treated.
>     The Van-Tonder implementation enforces declared import levels while the
>     Ghuloum-Dybvig implementation does not.  In other words, the Van-Tonder
>     implementation treats a reference to an identifier outside its declared
>     import levels as a syntax violation, while the Ghuloum-Dybvig
>     implementation ignores import level declarations, allowing references to
>     identifiers outside their declared import levels.  Both models are allowed
>     by R6RS.
> 
>     As a result, a working Van-Tonder library will be portable to the
>     Ghuloum-Dybvig system, but a working Ghuloum-Dybvig library will
>     not necessarily be portable to the Van-Tonder system.

 ...

>     The Van-Tonder implementation is in fact very close to the model
>     developed long ago by Matthew Flatt of PLT, with which there
>     is a large amount of historical experience among the PLT
>     user base.  For more details on the model and the design reasons
>     behind it, see for example the article:
> 
>     Further http://citeseer.ist.psu.edu/flatt02composable.html