LL(k) ---- LL(1) Parsers

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LL(k) - Left to right, Leftmost derivation with k lookahead symbols

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.

LL(k) parser generators

Modern parser generators that generate LL parsers with multi-token lookahead include:

  1. ANTLR (old PCCTS)
  2. Coco/R
  3. JavaCC
  4. Parsec
  5. SLK
  6. Spirit Parser Framework

Please give a look at following document (definitions over LL(1) parsers and algorithm to construct table based LL(1)): Algorithm.pdf

Example of a LL(1) grammar and his table


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