PostScript is kind of like a cross between Forth and Lisp, but a lot more like Lisp actually. And its data structures, which also represent its code, are essentially s-expressions or JSON (polymorphic dicts, arrays, numbers, booleans, nulls, strings, names (interned strings), operators (internal primitives), etc.)

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

Not coincidentally, James Gosling designed the NeWS window system and implemented its PostScript interpreter, years before designing and implementing Java. And before that he designed and implemented "MockLisp" in his Unix version of Emacs, which he self effacingly described like: "The primary (some would say only) resemblance between Mock Lisp and any real Lisp is the general syntax of a program, which many feel is Lisp's weakest point."

https://news.ycombinator.com/item?id=29954778

James Gosling's Emacs Mocklisp was like FEXPRs on PCP, with support for prompting the user to supply omitted arguments.

https://news.ycombinator.com/item?id=14312249

DonHopkins on May 10, 2017 | parent | context | favorite | on: Emacs is sexy

Hey at least Elisp wasn't ever as bad as Mock Lisp, the extension language in Gosling (aka UniPress aka Evil Software Hoarder) Emacs.

It had ultra-dynamic lazy scoping: It would defer evaluating the function parameters until they were actually needed by the callee (((or a function it called))), at which time it would evaluate the parameters in the CALLEE's scope.

James Gosling honestly copped to how terrible a language MockLisp was in the 1981 Unix Emacs release notes:

https://archive.org/stream/bitsavers_cmuGosling_4195808/Gosl

12.2. MLisp - Mock Lisp

Unix Emacs contains an interpreter for a language
that in many respects resembles Lisp. The primary
(some would say only) resemblance between Mock Lisp
and any real Lisp is the general syntax of a program,
which many feel is Lisp's weakest point. The
differences include such things as the lack of a
cons function and a rather peculiar method of
passing parameters.

"Rather peculiar" is an understatement. More info, links and code examples:

https://news.ycombinator.com/item?id=8727085

Comparison of PostScript with Forth and Lisp:

https://news.ycombinator.com/item?id=22456471

[...]

PostScript is much higher level than Forth, and a lot more like Lisp than Forth, and has much better data structures than Forth, like polymorphic arrays (that can be used as code), dictionaries (that can be used as objects), strings, floating point numbers, and NeWS "magic dictionaries" that can represent built-in objects like canvases, processes, events, fonts, etc.

Yet Forth doesn't even have dynamically allocated memory, although in a few pages of code you can implement it, but it's not standard and very few Forth libraries use it, and instead use the linear Forth dictionary memory (which is terribly limited and can't be freed without FORGETting everything defined after you allocated it):

https://donhopkins.com/home/archive/forth/alloc.f

PostScript is homoiconic. Like Lisp, PostScript code IS first class PostScript data, and you can pass functions around as first class objects and call them later.

https://en.wikipedia.org/wiki/Homoiconicity

[...]