Scala解析器和组合器:java.lang。RuntimeException:期望的字符串匹配regex ' \z'。

I am trying to parse some text following a grammer for Dynamic Epistemic Logic using Scala's RegexParser, as part of my Master Thesis. But I keep getting the same error on simple logical conjunctions. I understand where and why it's failing, but not why it's matching what it is in the first place.I am trying to parse some text following a gram