Question

I’m trying to find the maximum number within a list, then do something with it:

(defun maxList (l)
    (if (= (length l) 1)
            (first l)
        (if (> (first l) (maxList (rest l)))
            (first l)
            (maxList (rest l))
        );if
    );if
);defun


(defun try-let (l)
    (let (a (maxList l))
    (print a)
    );let
);defun

However it prints null, yet maxList works. What am I doing wrong ?

Answer 1

You’re missing a pair of parentheses:

(let ((a (maxList l)))

This is because let takes a list of bindings as in

(let ((a 1) (b 2) (c 'foo))
  expr)

so in this case you have to pass a one-element list containing the binding (a (maxList l))