Re: sum over list?

Frode Vatvedt Fjeld wrote:

(sum '(2 3 4)) => 9
(sum '(5 6)) => 11

 
The usual way of doing this would be
 
  (reduce #'+ '(2 3 4))
 
which is considered to be preferable to using APPLY. LOOP can do the
job almost as well:
 
  (loop for x in '(2 3 4) sum x)
 
The thing about LOOP is that it's much more flexible, in case you need
some slight variation of the theme, like for example:
 
  (loop for x in '(2 3 a 4) when (numberp x) sum x)

Gauche Scheme

(use gauche.lazy) ;; lfilter [lazy filtering]

(fold + 0 (lfilter number? '(2 3 a 4)))