The Marpa parser was intended to make the best results in the academic literature on Earley's algorithm available as a practical general parser. Earley-based parsers have had issues handling nullable symbols. Initially, we dealt with nullable symbols by following the approach in Aycock and Horspool's 2002 paper. This paper reports our experience with the approach in that paper, and the approach to handling nullables that we settled on in reaction to that experience.

翻译：Marpa Parser的用意是使关于Earley算法的学术文献取得最佳成果,作为实用的普通分析师;Earley的剖析员曾遇到处理无效符号的问题;最初,我们采用Aycock和Horspool2002年论文中的做法处理无效符号问题;本文报告了我们在该文件中的做法的经验,以及我们根据这一经验解决的处理无效符号的方法。</s>