Writing code for tests, on paper, has been a thing in CS for quite awhile. While writing lisp for tests, I used to sometimes write the code with no parens (using indentation to denote nesting). Then I'd go back and add parens where appropriate.

    defun add-pos-only v1 v2
        let sum 0
            if and > v1 0
                   > v2 0
                + v1 v2
                nil