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.
Ministry of Human Capacities, Hungary grant 20391-3/2018/FEKUSTRAT is acknowledged. Szabolcs Iván was supported by the János Bolyai Scholarship of the Hungarian Academy of Sciences. Kitti Gelle was supported by the ÚNKP-19-3-SZTE-86 New National Excellence Program of the Ministry of Human Capacities.
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