anchor.diff:                         (first b)
                          bindings))))))
   
  -
   ;;; unify/impl for strings
   
   (defmethod unify/impl ((a string) (b string) bindings)
  
positive.code:                                  x))))
      (if parsed-value
          (call-next-method tmpl
                            parsed-value)
          +fail+)))
                        
                          
  
negative.code: (defun unify (x y &optional (bindings +no-bindings+))
    (if bindings
        (unify/impl x y bindings)))
  
  ;;; unify/impl default implementation
  
  (defmethod unify/impl (a b bindings)
    (if (equal a b) bindings +fail+))
  
  
  ;;; unify/impl for wildcard
  