for( int i=0; i<epsilons.length; i++ )
epsilons[i] = Expression.epsilon;
// change current Acceptor to a new Acceptor.
// this new Acceptor is made to accept those satisfied rules only.
current = new ComplexAcceptor(
(REDocumentDeclaration)docDecl,
(ruleSet.length==0)?Expression.nullSet:Expression.epsilon,
epsilons, exps );
// call endElement to let Verifier do the job.