(define square-kernel
  (lambda (val)
    (* val val)))

(define square
  (lambda (val)
    (if (number? val)
        (square-kernel val)
        
(error 'square "I realize that this may be a biased viewpoint, but it appears to me that you've failed to enter something I consider a number.  While this may be my fault, I ask that you try to accomodate my world view."))))