Eberhard Bertsch (Ruhr University) & Mark-Jan Nederhof (Groningen University)
We recall the notion of regular closure of classes of languages. We present two important results. The first one is that all languages which are in the regular closure of the class of deterministic (context-free) languages can be recognized in linear time. This is a non-trivial result, since this closure contains many inherently ambiguous languages.
The second one is that the class of deterministic languages is contained in the closure of the class of deterministic languages with the prefix property, or stated in an equivalent way, all LR(k) languages are in the regular closure of the class of LR(0) languages.