[Maxima-discuss] progress on Maxima console display using Unicode characters

[Robert D. <rob...@gm...>]

I've made some progress on getting the Maxima console display (pretty
printer) to use Unicode characters in the interest of greater clarity. I've
captured some examples in a screenshot so that everyone sees the same thing.

[image: maxima-unicode-display-work-in-progress-2023-11-17.png]

These examples were composed with Maxima + SBCL; same results for Maxima +
Clisp. I am running Maxima in GNOME Terminal (Ubuntu Linux).

The hard part of this stuff is accounting for various use cases. Is the
Lisp implementation Unicode-capable? Most are, but not GCL. What if the
user wants to go back to the ASCII art display? I created a global flag
maxima_unicode_display to allow for that. What if the Lisp implementation
is capable but Unicode is disabled (e.g. because LANG does not designate a
UTF-8 locale)? Clisp is the only example I know about; I handled that, I
supposed if there are any others, we'll handle them case by case.

The biggest question to me at present is how to handle the various display
characters, e.g. absboxchar, boxchar, rmxchar, lmxchar, etc. I can't bring
myself to introduce ASCII and Unicode variants of all those. Two solutions
I can handle, conceptually speaking, are to apply those only when
maxima_unicode_display is false, or just nuke them entirely, so that
maxima_unicode_display = false has fixed characters for drawing.

I would like to take this opportunity to emphasize that I DO NOT INTEND
THAT THE USER MUST ALWAYS USE UNICODE CHARACTERS AND FOR ALL LISP
IMPLEMENTATIONS. Sorry for shouting; I feel obliged to avoid
misunderstandings.

I have put the code I worked on so far on the
branch dodier-maxima-unicode-display, comprising one commit at
present, a856cbf, if anyone wants to take a look.

This work is inspired by the patch suggested by Frederic Chapoton on the
project web site. Thanks, Frederic! I have gone somewhat farther in hope of
resolving some of the usability issues. See:
https://sourceforge.net/p/maxima/feature-requests/185/

I don't remember for sure if anyone has worked on similar stuff in years
past; if so, maybe someone can point it out.

All the best,

Robert