I've noticed in recent years that my favorite (three) languages share some things in common:
* None of them are "mainstream" or "standard" (which, for those who know history, basically means: not *Algol* based)
* All of them work within their own "image" or environment.
* The idea of a "stand-alone executable" is a anethema and an alien concept.
* All of them encourage "rapid prototyping"
* All of them encourage programming "from the bottom up"
* All of them strongly encourage "small" programming units.
* And: all three of them incorporate totally different programming models :-)
What three are they? LISP (of course)..... and FORTH, and Smalltalk. I didn't put all these factors together until about a year ago.
So: what are *your* favorite concepts in LISP (and other languages)?
I might add I'm a real fan of OOP, so I'm bound to learn CLOS sooner or later....