This version quickly dumped Heap Exhaustion. The LABELS version does not, and can handle summation over lists much faster as well.
What does this mean? TCE only applies applies to local calls, therefore we should never write a "raw" recursive function? (which is a tad more elegant, imo). I haven't delved into TCOs deep enough to understand, but I had hoped that a smart compiler would be able to optimize the latter?
Comments
Thanks for that Scott, I've never heard of TCE -- learn something every day reading HN.
Just did a quick comparison (SBCL) between the above and the textbook version:
(defun sum (list) (if (null list) 0 (+ (car list) (sum (cdr list)))))
This version quickly dumped Heap Exhaustion. The LABELS version does not, and can handle summation over lists much faster as well.
What does this mean? TCE only applies applies to local calls, therefore we should never write a "raw" recursive function? (which is a tad more elegant, imo). I haven't delved into TCOs deep enough to understand, but I had hoped that a smart compiler would be able to optimize the latter?