2026-09-09 13:36 UTC
@sigue@universeodon.com @mdhughes@appdot.net @Ardubal@mastodon.xyz @vnikolov@ieji.de @screwlisp@gamerplus.org @kentpitman@climatejustice.social @nosrednayduj@hachyderm.io
In some early #Lisp systems I have played with, it was possible *but not advisable* to rebind both `NIL` and `T`.
Replies (1)
-
@nosrednayduj@hachyderm.io 2026-09-10 19:08
@simon_brooke@mastodon.scot @sigue@universeodon.com @mdhughes@appdot.net @Ardubal@mastodon.xyz @vnikolov@ieji.de @screwlisp@gamerplus.org @kentpitman@climatejustice.social I vaguely recalled error messages from lucid lisp when you tried to change T and NIL, so I asked my partner who remembered better. He says: As I recall the errors were "Veritas Aeterna -- can't setq T" and "Nihil ex nihil -- can't setq NIL". The latin in the latter is wrong; it should be "Nihil ex nihilo", but the above is what I remember. This may date back to Maclisp. In Common Lisp there are constants that can't be set, so you don't really need special messages for T and NIL.