Walter Bucher

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In this no te we answer an open qiuestion in the theory of grammarical complexity: We show that if L is an infinite context-free language, then L,, the set of words in L of length less than or equal to n can be generated by O(IE,, 12’3) cosxt-free productions, and if L is an infinite linear language, then L, can be generated by Ol:&,I> 1’ mear productions.(More)
A dual bordered OS system is a triple (∑, P, S) where ∑ is a finite alphabet, S a finite subset of ∑*, the set of axioms, and P a finite set of rules of the form a→a × a, where a ε ∑ and x ε ∑ *. Using well-quasi-order theory, we show that the regularity problem for such systems is decidable. Whether such a system generates a regular language essentially(More)