Abstract
Let G be a context-free grammar and let L be the language of all the words derived from any variable of G. We prove the following generalization of Higman’s theorem: any division order on L is a well quasi-order on L. We also give applications of this result to some quasi-orders associated with unitary grammars.
This work was partially supported by MIUR project “Linguaggi formali e automi: teoria e applicazioni”.
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D’Alessandro, F., Varricchio, S. (2003). On Well Quasi-orders on Languages. In: Ésik, Z., Fülöp, Z. (eds) Developments in Language Theory. DLT 2003. Lecture Notes in Computer Science, vol 2710. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-45007-6_18
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DOI: https://doi.org/10.1007/3-540-45007-6_18
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