(define (pmatch el)
   (lambda (parser)
     (p-cond parser
         ((lambda (parser)
             (if (eqv? (p-car parser) el)
             (p-advance parser)
             (p-fail-parser parser)))))))
(define (pmany op)
   (lambda (parser)
      (letrec ((loop (lambda (cur-stream)
            (let ((p-next (op cur-stream)))
               (p-cond p-next
                   (loop
                    p-succ-parser
                    p-succ-parser
                    ))))))
     (loop parser))))