Design patterns for parsing


We provide a systematic transformation of an LL(1) grammar to an object model that consists of <ul><li>an object structure representing the non-terminal symbols and their corresponding grammar production rules,</li> <li>a union of classes representing the terminal symbols (tokens).</li></ul>We present a variant form of the visitor pattern and apply it to the above union of token classes to model a predictive recursive descent parser on the given grammar. Parsing a non-terminal is represented by a visitor to the tokens. For non-terminals that have more than one production rule, the corresponding visitors are chained together according to the chain of responsibility pattern in order to be processed correctly by a valid token. The abstract factory pattern, where each concrete factory corresponds to a non-terminal symbol, is used to manufacture appropriate parsing visitors.Our object-oriented formulation for predictive recursive descent parsing eliminates the traditional construction of the predictive parsing table and yields a parser that is declarative and has minimal conditionals. It not only serves to teach standard techniques in parsing but also as a non-trivial exercise of object modeling for objects-first introductory courses.

DOI: 10.1145/1047344.1047497

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@inproceedings{Nguyen2005DesignPF, title={Design patterns for parsing}, author={Dung Zung Nguyen and Mathias Ricken and Stephen B. Wong}, booktitle={SIGCSE}, year={2005} }