anchor.diff:          ((and (bignump x)
                 (bignump y))
            (%%bignum-* x y))
  -        (t (error "Argument combination not supported."))))
  +        (t (check-type x number)
  +           (check-type y number)
  +           (error "Argument combination not supported."))))
  
positive.code:         ((and (bignump x)
                (bignump y))
           (%%bignum-- x y))
          (t (error "Argument combination not supported."))))
  
  ;; Cheating here as well... Only deals with 1 word bignums.
  (define-lap-function %%bignum-* ()
  
negative.code:     rem))
  
  (defun generic-+ (x y)
    (cond ((and (fixnump x)
                (fixnump y))
           (error "FIXNUM/FIXNUM case hit GENERIC-+"))
          ((and (fixnump x)
                (bignump y))
           (%%bignum-+ (%make-bignum-from-fixnum x) y))
          ((and (bignump x)
                (fixnump y))
           (%%bignum-+ x (%make-bignum-from-fixnum y)))
          ((and (bignump x)
                (bignump y))
           (%%bignum-+ x y))
          (t (check-type x number)
             (check-type y number)
             (error "Argument combination not supported."))))
  
  (define-lap-function %%bignum-- ()
    ;; Save on the lisp stack.
  