+1 for Emacs. Some people do not realize this, but the thing you build when you compile an Emacs distribution is not a text editor. It's just a specialized li

+1 for Emacs. Some people do not realize this, but the thing you build when you compile an Emacs distribution is not a text editor. It's just a specialized lisp interpreter that has primitives for handling things like frames, buffers, and other UI-type stuff like detecting key chords, plus some math and stringy stuff, and a few other bits and bobs. The editor itself is written in Elisp. To illustrate, this is what I get when I run `sloccount` on the source download of Emacs 28.2 from gnu.org: Totals grouped by language (dominant language first): lisp: 1253948 (75.66%) ansic: 368126 (22.21%) objc: 17115 (1.03%) sh: 7261 (0.44%) cpp: 1851 (0.11%) yacc: 1566 (0.09%) perl: 1442 (0.09%) php: 1035 (0.06%) pascal: 1011 (0.06%) python: 993 (0.06%) awk: 781 (0.05%) cs: 770 (0.05%) ada: 725 (0.04%) ruby: 405 (0.02%) erlang: 153 (0.01%) java: 65 (0.00%) tcl: 16 (0.00%) It's basically 75% elisp, 25% C, and more or less all of that C code is either implementing the lisp interpreter itself, or interfacing to system libraries. Using Emacs is really the closest you can get these days to working on one of the old LISP machines from the 80s, except it's more fun.