PostScript is as truly homoiconic and polymorphic and interactive as Lisp.

And by truly homoiconic I mean not trivially and uselessly homoiconic like TCL, where "everything is a string".

And at the same time it's "JSONic" in the sense that it supports the full range of JSON data types, and is polymorphic in the sense that objects (as opposed to variables, arrays elements, and dict slots) have type and can contain objects of different types (unlike Forth, which is untyped, and is also commonly compared to PostScript because they're both stack based).

But of course PostScript was designed decades before JSON was a thing. However, the point is that Lisp S-Expressions don't directly support polymorphic dictionaries, but PostScript (and JavaScript/JSON, and Python) do.

The PostScript-based NeWS window system:

1) Used PostScript code instead of JavaScript
for programming.

2) Used PostScript graphics instead of DHTML and CSS
for rendering.

3) Used PostScript data instead of XML and JSON
for data representation.

And PostScript (and thus NeWS) also has an interactive REPL like Lisp, to support live and exploratory programming. Imagine being able to telnet to an X11 server and create windows and draw on them interactively!

PostScript is not only homoiconic, but also point-free (or "tacit"), like Forth!

https://en.wikipedia.org/wiki/Tacit_programming#Stack-based

https://en.wikipedia.org/wiki/Talk%3AHomoiconicity#PostScrip...

https://news.ycombinator.com/item?id=18317280

>The beauty of your functional approach is that you're using PostScript code as PostScript data, thanks to the fact that PostScript is fully homoiconic, just like Lisp! So it's excellent for defining and processing domain specific languages, and it's effectively like a stack based, point free or "tacic," dynamically bound, object oriented Lisp!

The fact that PostScript code IS PostScript data, without any intermediate AST representation or reflection API, means that a PostScript data structure editor is also a code editor.

PostScript's homoiconicity and interactivity (plus the fact that PostScript is great at drawing scalable text and graphics) makes it easy to make a visual programming language and debugger interface for PostScript, with a graphical direct manipulation REPL loop that supports "direct stack manipulation" by dragging objects on and off the stack, and editing code and data by drag-and-drop and cut-and-paste.

PSIBER Space Deck Demo

https://www.youtube.com/watch?v=iuC_DDgQmsM

>Demo of the NeWS PSIBER Space Deck. Research performed under the direction of Mark Weiser and Ben Shneiderman. Developed and documented thanks to the support of John Gilmore and Julia Menapace. Developed and demonstrated by Don Hopkins.
Described in "The Shape of PSIBER Space: PostScript Interactive Bug Eradication Routines".

The Shape of PSIBER Space: PostScript Interactive Bug Eradication Routines — October 1989

https://donhopkins.medium.com/the-shape-of-psiber-space-octo...

Written by Don Hopkins, October 1989.
University of Maryland Human-Computer Interaction Lab, Computer Science Department, College Park, Maryland 20742.

Abstract:
The PSIBER Space Deck is an interactive visual user interface to a graphical programming environment, the NeWS window system. It lets you display, manipulate, and navigate the data structures, programs, and processes living in the virtual memory space of NeWS. It is useful as a debugging tool, and as a hands on way to learn about programming in PostScript and NeWS.

PostScript Source Code Available Here:

https://www.donhopkins.com/home/pub/NeWS/litecyber/

Introduction:
Cyberspace. A consensual hallucination experienced daily by billions of legitimate operators, in every nation, by children being taught mathematical concepts … A graphic representation of data abstracted from the banks of every computer in the human system. Unthinkable complexity. Lines of light ranged in the nonspace of the mind, clusters and constellations of data. Like city lights, receding …. [Gibson, Neuromancer]

The PSIBER Space Deck is a programming tool that lets you graphically display, manipulate, and navigate the many PostScript data structures, programs, and processes living in the virtual memory space of NeWS.

The Network extensible Window System (NeWS) is a multitasking object oriented PostScript programming environment. NeWS programs and data structures make up the window system kernel, the user interface toolkit, and even entire applications.

The PSIBER Space Deck is one such application, written entirely in PostScript, the result of an experiment in using a graphical programming environment to construct an interactive visual user interface to itself.

It displays views of structured data objects in overlapping windows that can be moved around on the screen, and manipulated with the mouse: you can copy and paste data structures from place to place, execute them, edit them, open up compound objects to see their internal structure, adjust the scale to shrink or magnify parts of the display, and pop up menus of other useful commands. Deep or complex data structures can be more easily grasped by applying various views to them.

[...]