Shouldn't it be (+ a (apply + b))
Almost. It should be (+ a (apply #'+ b)). Common Lisp is a Lisp-2, so a + in the argument position is assumed to be a variable named +, not the function named +, unless you specify otherwise.
alt Hacker News
Almost. It should be (+ a (apply #'+ b)). Common Lisp is a Lisp-2, so a + in the argument position is assumed to be a variable named +, not the function named +, unless you specify otherwise.