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Avoiding Latch Formation in Regular Expression Recognizers

Department of Computer Science, Columbia University
Publication Date
  • Computer Science
  • Design


Specialized silicon compilers, or module generators, are promising tools for automating the design of custom VLSI chips. In particular, generators for regular language recognizers have many applications. A problem called latch formation that causes regular expression recognizers to be more complex than they would first appear is identified. if recognizers are constructed in the most straightforward way from certain regular expressions, they may contain extraneous latches that cause incorrect operation. After identifying the problem, the article presents a source-to-source transformation that converts regular expressions that cause latch formation into expressions that do not. This transformation allows regular expression recognizers to be simpler, smaller, and faster, thus adding to the advantages of specialized silicon compilers.

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