Question

I want to sum the numbers in a list without using recursion. I know you can sum a list of numbers like this

(+ num1 num2 … numN)

but what if you have a list L which equals to ‘(num1 num2 … numN)
is there a way to make + take the numbers in this list as arguments. I need to do this without recursion or helper functions.

Answer 1

Sure, just use apply:

(apply + '(1 2 3 4 5 6))   ; same as (+ 1 2 3 4 5 6)
(apply + 1 2 3 '(4 5 6))   ; ditto
(apply + 1 2 3 4 5 '(6))   ; ditto
(apply + 1 2 3 4 5 6 '())  ; ditto