anchor.diff:                          ;; remove all but the expressions whose value is the same as lhs-expr
                           (remove lhs-expr (make-exprs rhs)
                             :test-not #'eql
  -                          :key #'eval))
  +                          :key #'eval)))
                 (make-exprs lhs))
         (mapcan (lambda (rhs-expr)
                   (mapcar (lambda (lhs-expr)
  
positive.code:                         ;; remove all but the expressions whose value is the same as rhs-expr
                          (remove rhs-expr (make-exprs lhs)
                            :test-not #'eql
                            :key #'eval))))
                (make-exprs rhs))))
  
  (defun make-exprs (numbers)
  
negative.code:       (loop for i from 1 to (1- (length numbers))
              for partition = (split numbers i) append 
            (loop for arg1 in (make-exprs (car partition)) append 
                (loop for arg2 in (make-exprs (cadr partition)) append 
                  (apply-binary-ops arg1 arg2))))))
  
  (defun apply-unary-ops (arg1)
  