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On the space optimizing effect of eliminating single productions from LR parsers

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Summary

Single productions in the syntax of a programming language usually have no semantic significance, and thus parsers can be modified so that they do not perform reductions by single productions. In this paper we show that the basic method developed by Pager for eliminating all undesired single productions from LR parsers can cause a quadratic increase in the number of states of the parser. We then define an improvement of Pager's basic method such that generally smaller parsers are produced; in fact, even a quadratic decrease in the number of states is possible. This improvement is further evaluated by giving a sequence of practically motivated grammars for which substantial savings in space are obtained. We also characterize this improvement by a grammatical condition under which it is guaranteed that no increase in the number of states can occur. This condition is compared with a similar condition derivable in the case of Pager's original method.

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  1. Department of Computer Science, University of Helsinki, Tukholmankatu 2, SF-00250, Helsinki 25, Finland

    Eljas Soisalon-Soininen

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  1. Eljas Soisalon-Soininen
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Part of this work was carried out when the author was visiting the University of California, Department of Mathematics, at Santa Barbara as an ASLA Fulbright Scholar

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Soisalon-Soininen, E. On the space optimizing effect of eliminating single productions from LR parsers. Acta Informatica 14, 157–174 (1980). https://doi.org/10.1007/BF00288542

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  • DOI: https://doi.org/10.1007/BF00288542

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