That's very cool! I'd like to see more about how the debugger works. Are there any video demos available, please?

I love Glenn Reid's book, Thinking PostScript. It's like the Thinking Forth [1] of PostScript! ;) I always thought of PostScript as a cross between Lisp and Forth [2], but more in the Lisp camp, since it's so easy to write a metacircular evaluator [3] or a quine [4] in PostScript:

    {{[ exch /dup load /exec load ] cvx} dup exec}

Do you remember Glenn Reid's "Distillery" [5]? It's a PostScript program that optimized other PostScript programs, which you prepended before your PostScript print file, sent to a printer, and it partially evaluated the PostScript code in the print file. It then echoed back another highly optimized flat PostScript program that printed the exact same pages, all in one coordinate system, with superfluous graphics state changes removed. That glorious hack, based on John Warnock's idea of redefining the imaging operators, eventually evolved into PDF! [6]

Glenn also wrote a delightful "Font Appreciation" app for NeXT called TouchType [7], which decades later has only recently found its way into Photoshop.

I wrote a visual interactive PostScript debugging tool for NeWS called the PSIBER Space Deck [8], and the PseudoScientific Visualizer [9] for drawing PostScript data structures like NeWS object and class dictionaries or a network map of ARPANET IMPs, and a paper [10] about them. It was most useful for debugging itself, which was fortunate, since it was pretty buggy. I integrated the metacircular PostScript evaluator with the debugger, so you could single step through PostScript code, and draw graphics to visualize the program execution state. And I made my own NeWS distillery [11] "in the spirit of Glenn Reid's Distillery" ;), for making flat printable PostScript dumps of anything procedurally drawn on the screen, which I used for some of the illustrations in the paper [12].

[1] Thinking Forth: http://thinking-forth.sourceforge.net/

[2] PostScript -vs- Forth: http://donhopkins.com/home/code/ps-vs-forth.txt

[3] PostScript Metacircular Evaluator: http://donhopkins.com/home/code/ps.ps.txt

[4] PostScript Quine: http://donhopkins.com/home/archive/news-tape/fun/quine/quine

[5] Glenn Reid's PostScript Distillery: http://donhopkins.com/home/archive/postscript/newerstill.ps....

[6] The Distiller Story: http://blogs.adobe.com/insidepdf/2007/11/the_distiller_story...

[7] TouchType: https://ftp.nice.ch/peanuts/GeneralData/Usenet/news/1990/_CS...

[8] PSIBER Space Deck Demo: https://www.youtube.com/watch?v=iuC_DDgQmsM

[9] Pseudo Scientific Visualizer Demo: https://www.youtube.com/watch?v=_fqCeuue5Ac

[10] The Shape of PSIBER Space: PostScript Interactive Bug Eradication Routines: http://www.donhopkins.com/drupal/node/97

[11] NeWS Distillery: http://donhopkins.com/home/archive/news-tape/utilities/cyber...

[12] Distilled PostScript PseudoScientific Visualization of Arpanet IMPS: http://donhopkins.com/home/archive/news-tape/documents/psibe...