Re: RFC: User-defined pseudovectors

[Lars Brinkhoff <lars@nocrew.org>]

As long as you work inside Emacs, I agree there's no great need for
user-defined types, because Emacs Lisp already provides the data
structures that are commonly needed.  And you can pass around lists or
vectors which provides a 99% solution in most cases.

But with an FFI, I would argue that the situation changes.  When you
want to interface with code written in other languages, it seems to me
that the need increases.  Most other languages have some kind of
user-defined record types, and they are used quite liberally.

Stefan Monnier <monnier@iro.umontreal.ca> writes:
> I understand it might be handy for your Common-Lisp implementation,
> but you can already define your own `vectorp' to get the same result.

I don't see that I could define one which would accept any vector wich
any content, and be able to tell a "proper vector" apart from user-
defined types.

>>     (cond
>>      ((vectorp x)   (frob-vector x))
>>      ((foop x)      (frob-foo x))))
>
> So similarly the above code should check `foop' before `vectorp'.

That would still fail for the input [foo].

> Maybe the Guile guys are more likely to be wiling to make changes to
> their system in order to better support some other language.

No change is needed.  Guile already has user-defined record types,
which is exactly what I want.  Maybe I should just wait for
GuileEmacs, but as you wrote elsewhere its schedule is somewhat
undependable.