sly

Some combination of [0], [1], [2], and [3] is the closest modern equivalent. [0] https://slime.common-lisp.dev/ [1] https://github.com/joaotavora/sly [2] https://mcclim.common-lisp.dev/ [3] https://lem-project.github.io/ Also, Portable Genera is still being developed by a former Symbolics employee but unfortunately it is only available for a chosen few, at least for now.

Debugging is an extraordinarily first-class, up-front, frequent activity in Common Lisp, as the facilities are built into the language itself. While Lisp gets a lot of flak for basically (up to a few daring power-user exceptions) requiring Emacs, SLIME/SLY [1,2] are environments that will make you feel closer to your program than you get in other environments, including graphical IDEs. Given that the normal way to develop a Lisp program is to do it incrementally, your program (or someone else’s!) will break, and it will break often, and you’ll get launched into an interactive debugger. But it’s friendly, not requiring a completely separate, foreign toolchain, and much of the functionality works regardless of which editors/IDEs you’re using (though Emacs makes the experience much more ergonomic). I think this is perhaps a bigger selling po