Comment by bslatkin

For a very simple, single-expression lambda function I agree you don't need an explicit return. Even Python skips the "return" for lambdas. But for anything more complex, I find explicit returns, especially early returns, makes the code much more readable for people who are used to imperative languages.

For example, which of these is more clear to people who don't know Lisp? I'd argue the second one because of the early return if guard.

    ---- THIS ----

    (defun sum-helper (items total)
        (cond
            (items
                (sum-helper
                    (cdr items)
                    (+ total (car items))))
            (t total)))

    (defun sum (&rest items)
        (sum-helper items 0))

    (print (sum 1 2 3 4))

    ----- OR -----

    (defun sum-helper2 (items total)
        (if (not items)
            (return-from sum-helper2 total))

        (sum-helper2
            (cdr items)
            (+ total (car items))))

    (defun sum2 (&rest items)
        (sum-helper2 items 0))

    (print (sum2 5 6 7 8))