Zerteilungsverfahren mit unbeschraenkter Vorschau

SIGLETIB: RN 9815 (8005) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The Order Type of Scattered Context-Free Orderings of Rank One is Computable

A linear ordering is called context-free if it is the lexicographic ordering of some context-free language and is called scattered if it has no dense subordering. Each scattered ordering has an associated ordinal, called its rank. It is known that the isomorphism problem of context-free orderings is undecidable in general. In this paper we show that it is decidable whether a context-free ordering is scattered with rank at most one, and if so, its order type is effectively computable

Shift-Resolve Parsing: Simple, Unbounded Lookahead, Linear Time

This paper introduces a mechanism for combining unbounded lookahead exploration with linear time complexity in a deterministic parser. The ide

Linear Orders in the Pushdown Hierarchy

Abstract. We investigate the linear orders belonging to the pushdown hierarchy. Our results are based on the characterization of the pushdown hierarchy by graph transformations due to Caucal and do not make any use of higher-order pushdown automata machinery. Our main results show that ordinals belonging to the n-th level are exactly those strictly smaller than the tower of ω of height n +1. More generally the Hausdorff rank of scattered linear orders on the n-th level is strictly smaller than the tower of ω of height n. As a corollary the Cantor-Bendixson rank of the tree solutions of safe recursion schemes of order n is smaller than the tower of ω of height n. As a spin-off result, we show that the ω-words belonging to the second level of the pushdown hierarchy are exactly the morphic words.