Re: User-defined record types

[Stefan Monnier]

> Something that represents JSON and YAML well would be nice.  Currently
> we don't have an ELisp data structure that can preserve all JSON nuances
> without acrobatics (e.g. preserving the difference between "null" and
> "empty list" or the native JSON data types).

I don't understand what you mean here.  It's very easy to have special
values, e.g. (defconst json-null (make-symbol "json-null")).

IIUC The problem of json.el is that it wants to provide a bridge between
traditional Elisp data structures and JSON, and there is no reliable
two-way conversion between the two.
IIUC the current json.el focuses on making sure that converting to JSON
and back returns the same object.

But I don't see any technical difficulty writing a json2.el alternative
which focuses on "to Elisp and back", i.e. when it reads a JSON object
it returns an Elisp object that preserves all JSON nuances so that it
can be reliably converted back to the "exact same" JSON object.

> a native XML data structure would also be nice.  We have what libxml
> produces, dumped in an awkward tree, but nothing native.

Not sure what "native" can mean in this context: we were talking about
new Lisp-defined types.

Whereas you seem to be talking about getting access to objects defined
in other (non-Lisp) libraries, i.e. an FFI.

Or maybe you're just talking about a more efficient representation for
an XML/JSON tree.  If Lisp-defined data types could offer that, it would be
great, of course, but I personally don't see how that would work.


        Stefan