Xerox controlled the whole stack, they invented it for their systems.
So these workstations where an whole stack OS.
You can read about their implementations on the links I provided before.
Additionally, you can get the original Smalltalk-80 from from Stephane's web site.
http://stephane.ducasse.free.fr/FreeBooks.html
This is a very ruft idea how it felt to use a Smalltalk workstation:
https://www.youtube.com/watch?v=8yxCJfayW-8
https://www.youtube.com/watch?v=JLPiMl8XUKU
The REPL was what is known in Smalltalk as transcript.
Similarly the Interlisp-D workstation also had they own mixture of REPL and editing
https://www.youtube.com/watch?v=wlN0hHLZL8c
Some of the ideas that lived on the Lisp Machines afterwards
https://www.youtube.com/watch?v=NOysrxexTXg
https://www.youtube.com/watch?v=o4-YnLpLgtk
Mesa was a memory safe system programming language created at Xerox, as an evolution from Extended Algol to replace BCPL. Niklaus Wirth based his Modula-2 design on it.
Shortly thereafter they updated Mesa into Cedar, which added support for RC with local GC for cycle collection. The system then got called Mesa/Cedar.
It allowed the same interactive experience as the other workstations, but using a GC enabled systems programming language.
The REPL provided nice features, like auto-suggestion when a typo would cause a compilation failure. It is also probably the first graphical debugger for a strong typed language.
Any OS API could be used on the REPL by typing modulename.procedure , which could use other OS APIs to get its input from different sources.
An idea Wirth adopted into Oberon.
You can see how all three environments looked like here:
http://www.chilton-computing.org.uk/inf/literature/books/wm/...
And yes, Powershell alongside .NET is probably the closest we have in modern computers to those systems.
Followed by Swift Playgrounds and AppleScript on Apple systems.
Although Apple also provided similar experiences with Common Lisp, Hypercard and their NewtonScript and Dylan.