Tagged code generation
One of the most distinctive features of Common Lisp and Lisp in general, are its code-generation and code-manipulation capabilities.
Probably the best example is the
LOOP macro - a Swiss Army knife of iteration that can do pretty much anything. The following snippet iterates a list of random numbers collecting some statistics of its contents and does that while being very concise and readable:
(let ((random (loop with max = 500 for i from 0 to max collect (random max)))) (loop for i in random counting (evenp i) into evens counting (oddp i) into odds summing i into total maximizing i into max minimizing i into min finally (format t "Stats: ~A" (list min max total evens odds))))
Stats: (0 499 120808 261 240)