4 Nov 2001 23:54:14 -0500

Related articles |
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LR(0) and Lookaheads willverine@hotpop.com (Will) (2001-11-04) |

Re: LR(0) and Lookaheads thant@acm.org (Thant Tessman) (2001-11-08) |

Re: LR(0) and Lookaheads jjan@cs.rug.nl (J.H.Jongejan) (2001-11-08) |

From: | "Will" <willverine@hotpop.com> |

Newsgroups: | comp.compilers |

Date: | 4 Nov 2001 23:54:14 -0500 |

Organization: | Excite@Home - The Leader in Broadband http://home.com/faster |

Keywords: | parse, LR(1) |

Posted-Date: | 04 Nov 2001 23:54:14 EST |

The new dragon book gives an algorithm for constructing parsing tables

for LR(1) grammars. The '1' is suppose to be 1 lookahead. If you can

construct such an LR(1) parsing table without conflicts for a given

grammar, then the grammar is LR(1) grammar.

Is lookahead and the current input symbol the same thing?

I had thought that LR(0) was just another way of saying SLR(1) because

in constructing SLR(1) grammars, LR(0) items are used. However I am

wrong. As a matter of fact, LR(0) grammars are "smaller" than SLR(1)

grammars. So how do I test a grammar to see if it is LR(0) grammar

(i.e. where in the new dragon is this explained ... how do you

construct a LR(0) parsing table)? Also the '0' in LR(0) grammars means

0 lookahead? That does not make sense, unless I am not understanding

what lookahead means. If you don't look at any input symbols, how are

you suppose to parse the input string?

Thanks in advance.

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