I was an AI student at MIT in the 1970s. Like every other student, I thought language was paramount. Nevertheless, Lisp was the primary language. These are some things I still think it is pretty good for:
Symbolic math. It is easy and instructive to write symbolic differentiation of an expression, and algebraic simplification. I still do those, even though I do them in C-whatever.
Theorem proving. Every now & then I go on a temporary AI binge, like trying to prove that insertion sort is correct. For that I need to do symbolic manipulation, and I usually fall back on Lisp.
Little domain-specific-languages. I know Lisp isn't really practical, but if I want to try out a little DSL without having to get all wrapped up in parsing, etc., Lisp macros make it easy.
Little play algorithms like minimax game tree search can be done in like three lines.
- Want to try lambda calculus? It's easy in Lisp.
Mainly what Lisp does for me is mental exercise. Then I can carry that over into more practical languages.
P.S. Speaking of lambda calculus, what also started in the 1970s, in that same AI millieu, was that OO started invading everybody's brain, and somehow, interest in what it is seems to have crowded out much interest in what it is good for. I.e. work on machine learning, natural language, vision, problem solving, all sort of went to the back of the room while classes, messages, types, polymorphism, etc. went to the front.
