Re: [Texmacs-dev] Problem with the scheme_tree format.

[Joris van der Hoeven]

> The scheme_tree, to which is converted any parameter declared of type
> "tree" in the build-glue-*.scm files, is broken.
> 
> The problem is that it is too poorly structured. The only tree_label
> used are TUPLE and STRING. Symbols are represented by unquoted strings
> and strings are represented by quoted strings.
> 
> That is confusing and led to at least one problem with the
> get-inverse-binding command. To get the binding associated to a symbol,
> say "<leftarrow>" the string (which is a so-called "universal symbol"
> but is actually a string for all practical purpose) the GUILE program
> must first convert it to a Scheme symbol...
> 
> Furthermore, the scheme_tree format cannot represent Scheme characters
> or booleans. The only literals it can represent are numbers, symbols
> and strings. That is very annoying since chars and booleans, which are
> types which do provide interesting (because safe) semantics cannot be
> used in server commands.

I agree that the current way to do things is not optimal and
we probably need a real "scheme" type, which would be able to
represent scheme expressions inside TeXmacs in a safe way
(both for the TeXmacs and guile kind of counting).

Nevertheless, the scheme_tree's are useful: they yield a uniform
way to *convert* any scheme expression *without* particular types
as a TeXmacs tree *without* inner nodes other than TUPLE.