Re: r6rs libraries

["Julian Graham" <joolean@gmail.com>]

Happy New Year, Guilers!


> So maybe I'm being dense here, but it looks like the way forward might
> be to whip up a quick module-to-library mapping system (i.e.,
> something like (foo bar (version)) -> /foo/bar/version) and then start
> working on piecemeal attempts to get imports working?  Like, in the
> following order, I'd say we could tackle:
>
> 1) Mapping the existing features of Guile's module system onto their
> R6RS counterparts
> 2) Implementing version selection
> 3) Implementing import levels

That last email was written between drinking at a bar and going to
bed.  The *proper* mapping for versions would be more like:

(foo bar (version)) -> (foo version bar)

So if your R6RS library name was `(my r6rs library (1 2 3))', then the
corresponding Guile module name would be `(my r6rs 1 2 3 library)'.

I had a little time this afternoon to play around with some syntax
transformations for converting between libraries and modules, which
led to the following observations:

* Any library-to-module transformations we could do would be one-way
(i.e., libraries to modules), since R6RS requires that any non-binding
expressions have to come after the bindings in a library; rewriting a
module to meet that requirement would be non-trivial.

* Module definitions created from R6RS libraries need to use the #:pure keyword.

* There's a somewhat perplexing R6RS requirement to allow renaming
symbols on export, similar to the way Guile currently supports
renaming them on import.  I don't see a way to do this without
modifications to the core.

* I think it'd be possible to implement R6RS "import levels" using
Guile's existing #:export, #:export-syntax, #:reexpport, and
#:reexport-syntax keywords -- if it weren't for the `(meta <level>)'
option for import specifiers.  It might still be possible, given the
allowances of section 7.2.  I don't know, I'm still trying to figure
that out.

Other than the above, it looks like a lot of the heavy lifting has
already been done by the module system.


Regards,
Julian