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)

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