James Gosling on Richard Stallman [video]
From a 2002 Stallman lecture:<p><i>There was no free software Emacs editor that ran on Unix. I did, however, have a friend who had participated in developing Gosling&#x27;s Emacs. Gosling had given him, by email, permission to distribute his own version. He proposed to me that I use that version. Then I discovered that Gosling&#x27;s Emacs did not have a real Lisp. It had a programming language that was known as ‘mocklisp’, which looks syntactically like Lisp, but didn&#x27;t have the data structures of Lisp. So programs were not data, and vital elements of Lisp were missing. Its data structures were strings, numbers and a few other specialized things.<p>I concluded I couldn&#x27;t use it and had to replace it all, the first step of which was to write an actual Lisp interpreter. I gradually adapted every part of the editor based on real Lisp data structures, rather than ad hoc data structures, making the data structures of the internals of the editor exposable and manipulable by the user&#x27;s Lisp programs.<p>The one exception was redisplay. For a long time, redisplay was sort of an alternate world. The editor would enter the world of redisplay and things would go on with very special data structures that were not safe for garbage collection, not safe for interruption, and you couldn&#x27;t run any Lisp programs during that. We&#x27;ve changed that since — it&#x27;s now possible to run Lisp code during redisplay. It&#x27;s quite a convenient thing.</i><p><a href="https:&#x2F;&#x2F;www.gnu.org&#x2F;gnu&#x2F;rms-lisp.en.html" rel="nofollow">https:&#x2F;&#x2F;www.gnu.org&#x2F;gnu&#x2F;rms-lisp.en.html</a>