Editing LL(k) ---- LL(1) Parsers
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| − | + | '''''LL(k''') - '''L'''eft to right, '''L'''eftmost derivation with '''k''' lookahead symbols'' | |
| + | <br><br> | ||
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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. | ||
| + | <br><br> | ||
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| + | == LL(k) parser generators == | ||
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| + | Modern parser generators that generate LL parsers with multi-token lookahead include: | ||
| + | # '''[http://eplmediawiki.di.uminho.pt/index.php/ANTLR ANTLR] (old PCCTS)''' | ||
| + | # '''[http://eplmediawiki.di.uminho.pt/index.php/CoCo/R Coco/R]''' | ||
| + | # '''JavaCC''' | ||
| + | # '''Parsec''' | ||
| + | # '''SLK''' | ||
| + | # '''Spirit Parser Framework''' | ||
| + | <br> | ||
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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 == | ||
| + | [http://eplmediawiki.di.uminho.pt/uploads/LittleGarden.pdf LittleGarden.pdf] | ||
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| + | [[Category:Basic Concepts]] | ||
