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Diagnostics on LALR(k) conflicts based on a method for LR(k) Testing

  • Part I. Computer Science
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Abstract

A user of an LALR(k) parser generator system may have difficulties in understanding how a given LALR(k) conflict is generated. This is especially difficult if the conflict does not correspond to an LR(k) conflict.

A practical method for giving informative diagnostics on LALR(k) conflicts is presented. The diagnostics distinguish between those LALR(k) conflicts that correspond to LR(k) conflicts and those that do not. As a side effect the user is thus informed whether or not his grammar is in fact LR(k) despite not being LALR(k).

The method is based on an algorithm for testing LR(k)-ness using the LR(0) machine supplied with LALR(k) lookahead sets. This algorithm is presented and its correctness is proved.

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Authors and Affiliations

  1. Aalborg University Center, Aalborg, Denmark

    Bent Bruun Kristensen & Ole Lehrmann Madsen

  2. Computer Science Department, Aarhus University, Aarhus, Denmark

    Bent Bruun Kristensen & Ole Lehrmann Madsen

Authors
  1. Bent Bruun Kristensen
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  2. Ole Lehrmann Madsen
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Kristensen, B.B., Madsen, O.L. Diagnostics on LALR(k) conflicts based on a method for LR(k) Testing. BIT 21, 270–293 (1981). https://doi.org/10.1007/BF01941463

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  • DOI: https://doi.org/10.1007/BF01941463

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