# Questions tagged [lr-k]

LR(k) is a common type of parser for context-free grammars

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### Number of DCFG parse tree nodes with respect to input length

I read the question and answer at Number of nodes of a parse tree when the Grammar is in CNF?, and I'm curious about a related matter: obviously with a unrestrained LR grammar (as opposed to CNF) the ...
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### Any reference implementation of PCC algorithm out there?

Currently I'm exploring LALR(1) lookahead generation algorithms to implement. I've implemented Aho and Ullman one from their textbook, but recently stumbled upon "A new analysis of LALR ...
1 vote
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### Equivalence of LR(k) and LL(k′) parsers

Are there languages that can be parsed by an LR(k) parser but not by an LL(k′) parser for any k′?
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### Determine if two LR(1) action/goto tables always produce the same derivation

I am experimenting with implementing minimal LR(1) algorithms/techniques, but I find it very difficult to verify the correctness of what I've implemented. Is there a fast algorithm to determine if ...
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### Is THEADS the same as FIRST?

I'm reading the paper "A Practical General Method for Constructing LR(k) Parsers" by David Pager, and it contains the following paragraph: We will first of all briefly review the LR(1) ...
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1 vote
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### How to remove empty strings a.k.a (lambda, epsilon) from a LR(0) grammar

Say I have the following grammar: E -> TE' E' -> +TE'| -TE' | λ T -> (E) | id I need to build the finite state machine with the LR(0) items, But I ...
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### Item lookaheads versus dot lookaheads for $LR(k)$ with $k \gt 1$?

I was reading "Parsing Techniques: A Practical Guide, Second Edition" by Grune and Jacobs, which details a bunch of different parsing algorithms. In the section on $LR(2)$ parsing, they mention that ...
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### An intuitive explanation for LR grammars?

With LL grammars, there seems to be a very intuitive explanation, in terms of first and follow tables.( The first letter/s encountered in a particular state, can only mean a particular rule). With LR ...
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### Use DFA minimization on LR(1) states

I have recently started reading more about context-free parsing techniques, in particular LR parsing. As I have read, LR state transition graph (or table(s)) used for finding handles in sentential ...
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1 vote
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### How equality of item (production state) is defined in LR parser?

Whenever I read about equality I took it for granted, but few days ago I wondered if my understanding is not too shallow. Consider such example (taken from: http://david.tribble.com/text/honalee.html):...
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### Chomsky NF or Greibach NF benefits for LR parser?

Are there any benefits of having grammar in CNF/GNF for LR parser? I have those in mind: total speed of creating a parser (that is time for creating CNF/GNF out of the grammar, and then creating ...
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