What is tail recursion?

Question

Whilst starting to learn lisp, I\'ve come across the term tail-recursive. What does it mean exactly?

Answer 1

Here is a Common Lisp example that does factorials using tail-recursion. Due to the stack-less nature, one could perform insanely large factorial computations ...

(defun ! (n &optional (product 1))
    (if (zerop n) product
        (! (1- n) (* product n))))

And then for fun you could try (format nil "~R" (! 25))