Difference between revisions of "LL(k) ---- LL(1) Parsers"

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'''''LL(k''') - '''L'''eft to right, '''L'''eftmost derivation with '''k''' lookahead symbols''
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An '''LL(k)''' parser is a top-down parser, that is, it decides which production to use by looking at the next k tokens. This means that an LL(k) grammar must not have a point where the alternative productions have the same prefix, and that a production cannot be left-recursive - the left hand side must always resolve to a terminal. In addition, an LL(k) grammar must have a fixed value of k. Most LL(k) parsers are actually LL(1) parsers that use lookahead trees where it's necessary to disambiguate rules.
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== LL(k) parser generators ==
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Modern parser generators that generate LL parsers with multi-token lookahead include:
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# '''[http://eplmediawiki.di.uminho.pt/index.php/ANTLR ANTLR] (old PCCTS)'''
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# '''[http://eplmediawiki.di.uminho.pt/index.php/CoCo/R Coco/R]'''
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# '''JavaCC'''
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# '''Parsec'''
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# '''SLK'''
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# '''Spirit Parser Framework'''
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Please give a look at following document (definitions over LL(1) parsers and algorithm to construct table based LL(1)): [http://eplmediawiki.di.uminho.pt/uploads/AlgorithmLL1.pdf Algorithm.pdf]
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== Example of a LL(1) grammar and his table ==
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[http://eplmediawiki.di.uminho.pt/uploads/LittleGarden.pdf LittleGarden.pdf]
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[[Category:Basic Concepts]]
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Latest revision as of 01:31, 12 April 2014

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