Tunnel Parsing with Ambiguous Grammars

The article proposes an addition to the tunnel parsing algorithm that enables it to parse grammars having countable repetitions and configurations of grammar elements generating empty words without refactoring the grammar. The equivalency of trees built by the use of ambiguous grammar is discussed. The class of the ε-ambiguous grammars is defined as a subclass of the ambiguous grammars relative to these trees. The ε-deterministic grammars are then defined as a subclass of the ε-ambiguous grammars. A technique for linearly parsing on the basis of non-left recursive ε-deterministic grammars with the tunnel parsing algorithm is shown.