Re: Proper namespaces in Elisp

[Daniel Colascione]

On 5/8/20 11:59 AM, Vladimir Sedach wrote:
> Daniel Colascione <address@hidden> writes:
> > Common Lisp does deal with this problem in some cases, e.g., in LOOP.
> > We should be moving forwards keywords anyway.
>
> LOOP would not even have to deal with that if namespaces were over
> bindings, like Andrea suggested, and what Scheme module systems do.
>
> > FWIW, I think elisp should just literally copy Common Lisp's
> > approach.
>
> Please see this other sub-thread where I explain why this is a really
> bad idea:
>
> https://lists.gnu.org/archive/html/emacs-devel/2020-05/msg00623.html
>
> > It's tried and tested, and the pitfalls are well-understood.
>
> Well-understood enough where people want to throw away most of how it
> does namespace imports, and have a backward-compatible replacement
> ready this year:
>
> https://gist.github.com/phoe/2b63f33a2a4727a437403eceb7a6b4a3

I wouldn't call package-local nicknames "throw[ing] away" the namespace 
system. The post describes a logical extension. Is your argument that 
the CL namespace system (suitably extended) *allows* people to do silly 
things (like :use) even though it doesn't require that they do?

> There is no need to repeat the same mistakes. Andrea's proposal for
> namespacing over bindings/Scheme's approach avoids mangling the
> reader, does not cause problems for the printer, and does not make
> code resort to symbol-name hacks like LOOP does. Scheme's approach to
> namespacing has a lot of advantages over Common Lisp's.
>
> We can also avoid the "namespace multiple inheritance" problems of
> unintended re-definition and import conflicts if we combine João's
> approach of declaring prefixes with the ideas of package-local
> nicknames and namespaces over bindings.
>
> Here is how that might look:
>
> --8<---------------cut here---------------start------------->8---
> (declare-namespace jennys-awesome-string-library
>    (use elisp29)
>    (export foo))
>
> (declare-namespace jonnys-amazing-syntax-library
>    (use elisp29)
>    (export foo))
>
> (declare-namespace some-new-library
>    (use elisp30)
>    (import jennys-awesome-string-library st-)
>    (import jonnys-amazing-syntax-library sy-))

Fair enough. What about requiring that a colon separate the module 
prefix from the remainder of the symbol? Using a dash seems ripe for 
misinterpretation, but someone reading a symbol containing colon (in a 
way that looks vaguely reminiscent of CL) would know to look for a 
namespace alias instead of searching in vain for some global definition 
of st-foo or sy-foo.