A lower-bound for the number of productions required for a certain class of languages |
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Authors: | Brian Alspach Peter Eades Gordon Rose |
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Affiliation: | Department of Mathematics, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada;Department of Computer Science, University of Queensland, St. Lucia, Queensland, Australia 4067 |
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Abstract: | W. Bucher, K. Culik II, H. Maurer and D. Wotschke (Theoretical Computer Science 14(1981), pp. 227–246) posed the problem of producing the language Ln = {ab: 1≤a,b≤n and a≠b} with a minimal number of productions. Later, W. Bucher, K. Culik II and H. Maurer showed that productions are sufficient. In this note we show that productions are necessary for all n≥ 6. |
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