Question

I’m stuck on a homework question. I’m trying to define a function that checks if an element exist in a list using recursion. Below is what I have.

(defun is-member2 (X S)
"Check if a X is a member of S"
(if  (and (atom X) (not (null S)) (lisp S) (> (length S) 0))

    ;X- is a value, not a set
    (if (equal X (car S))

        ;Located
        (equal 'a 'a)

        ;NotLocated
        (is-memeber2 X (cdr S))

    )

    ;No- X is not a value
    ()
);end if
)

However, I keep on getting that is-memeber2 is undefined. This leads me to believe that either X is no longer a valid element or that (cdr S) is sending nul, but shouldn’t my if statement catch this?

Answer 1

is-member2 does not equal is-memeber2. Check your spelling.