Subject: Re: Q: total addition within an array. (any function or macro?) From: Erik Naggum <firstname.lastname@example.org> Date: 15 Dec 2000 17:42:47 +0000 Newsgroups: comp.lang.lisp Message-ID: <email@example.com> * firstname.lastname@example.org | One condition is, I don't know the total length of an array because it | will be changed every time. Maybe I could write down as (although it | looks complicated..), | | (setf total-value 0) | (loop for i from 0 to arr-index | do (setf total-value (+ total-value (aref arr i))) | finally (setf ave-value (/ total-value (+ arr-index 1)))) | | However, I just wonder that is there any function or macro which can | add whole values in an array? I want use this function with one | simple line.... I couldn't find that kind of things, but maybe | something exist? Thanks for advance. =) I should give you the hints and the pointers, but I'm tired, so here's how you compute the average of a vector of numbers: (/ (reduce #'+ <vector>) (length <vector>)) Incidentally, the standard deviation is also very useful if you ever work with averages: (let* ((mean (/ (reduce #'+ <vector>) (length <vector>))) (sdev (sqrt (/ (reduce #'+ <vector> :key #'(lambda (elt) (expt (- elt mean) 2))) (1- (length <vector>)))))) ...) As you may have noticed, this is idiomatic Common Lisp for the sum operator. #:Erik -- The United States of America, soon a Bush league world power. Yeee-haw!