Questions tagged [lr-k]

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

Filter by
Sorted by
Tagged with
0
votes
1answer
25 views

What to do following a reduce in LR(1) parsing?

I am using this standard question from Dragonbook as an example, (the first problem) . I have trouble with what happens in State 4 on LR(1) parsing. Once it is reduced by the rule C->d, now what ...
1
vote
0answers
20 views

Is there a direct way to obtain the RE for the handle-finding DFA of a grammar?

LR parser for a (CFG) grammar uses a handle-find automaton (which is a DFA) to find the handles. Such automata can be constructed by computing the canonical collection of sets of LR(0)/LR(1) items. Is ...
1
vote
1answer
27 views

What are cases where we cannot perform LR parsing without augmented grammar?

Many standard Compiler Design texts mention constructing augmented grammar as first step of LR parsing. The reason frequently is It is required in cases where start symbol comes on right hand of any ...
2
votes
1answer
79 views

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 ...
0
votes
1answer
19 views

Why shift means push terminal symbol and state into the stack? Why not push only state?

Shift means that you need to put the status and terminal symbol on the stack. But what is the terminal symbol used for? After all, if the reduce command is executed, both the state and the terminal ...
0
votes
1answer
24 views

How to create a LR(k) grammar for an arbitrary k

Is there a simple procedure for constructing a grammar that is LR(k) but not LR(k-1) for any k?
0
votes
1answer
277 views

Is following grammar LR(0)?

I know how to verify whether grammar is LR(0) or not. But this particular case is little tricky and hence the question. Grammar: $SL \rightarrow SL ; S \space | \space \epsilon$ $S \...
0
votes
2answers
259 views

Are shift and goto moves for all LR parsers ( LR(0), SLR(1),CLR(1),LALR(1) ) same?

I understand the difference in the parsing tables of the above 4 parsers. I understand that CLR>LALR>SLR>LR(0) in terms of power. Are shift and goto moves for all LR parsers ( LR(0), SLR(1),CLR(1),...
7
votes
2answers
1k views

DCFL with prefix property have LR(0) grammar?

There are two important theorems about LR(k) grammars and DCFL. Mentioned here. A language has an LR(1) grammar iff it is DCFL. A language has an LR(0) grammar iff it is DCFL and has prefix property. ...
0
votes
0answers
26 views

question about LL(1) and LR(0)

If grammar is an $LL(1)$ and does not contain any null production (i.e $V \rightarrow \epsilon$) then does that grammar necessarily be an $LR(0)$ grammar? I have tried to find counterexample for ...
0
votes
1answer
152 views

Analysis of a LALR shift-reduce conflict

I have created an extremely simple byacc grammar (ok, it's not really that simple but I simplified purposefully to be a minimal complete verifiable example): ...
1
vote
1answer
48 views

Wikipedia says this grammar is LR(0), but Grammophone says it is not; is it?

E -> E * B . E -> E + B . E -> B . B -> 0 . B -> 1 . I am confused because Wikipedia cites this grammar as an example of an LR(0) grammar ...
0
votes
1answer
98 views

Is there a LL(K) Grammar which is not LALR(K) Grammar?

It is easy to know that there are LALR(K) grammars which are not LL(K) because any grammar with left recursion which is LALR(K), is not LL(K) because all LL(K) grammar must be left recursion free. And ...
2
votes
1answer
621 views

When will SLR(1) parser fail but CLR(1) will not

Dragon book says following about where SLR(1) parser can fail but CLR(1) wont: Recall that in the SLR method, state $i$ calls for reduction by $A→α$ if the set of items $I_i$ contains item $[A→α.]$...
0
votes
1answer
297 views

LR parsers and ambiguous and non deterministic grammars

Dragon book says: An ambiguous grammar can never be LR. And then immediately further it says: For example, consider the dangling-else grammar: $\begin{align} stmt \rightarrow & \textbf{...
2
votes
1answer
664 views

What is handle in bottom up LR parsing?

I was taking course on compilers by Alex Aiken. You can find the slide discussing handles on this page. On the page of the slide, the instructor defines handle as follows: Assume a rightmost ...
1
vote
0answers
648 views

Are LL(1) grammars a subset of LR(0) grammars?

As far as I've understood it seems that LL1 are a subset of LR0, but studying the following grammar I end up in a contraddiction. Grammar : S -> (S) | [S] | {S} | ε This is an LL1 while it seems ...
1
vote
1answer
104 views
5
votes
1answer
724 views

can every LR(k) grammer be transformed to LR(1)

when i was studying compilers i came across this in Wikipedia every DCFL has a corresponding unambiguous grammar and hence can be parsed by an LR(1) parser which is the most powerful parser then what ...
2
votes
1answer
208 views

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 ...
1
vote
0answers
209 views

Is the Java 8 Grammar still a LALR(1) grammar?

As I found out here: http://www.eclipse.org/jdt/core/howto/generate%20parser/generateParser.html , the Java Version of 2005 (might be Java 6, I'm not sure) is a LALR(1) grammar. However, I couldn't ...
2
votes
0answers
166 views

Intuitive Explanation on Converting BNF Grammar to LR(1)

Consider the following BNF Grammar G: ...
4
votes
1answer
659 views

Are LR(k) languages and DCFLs equivalent?

In the familiar book of Theory of Computation by M. Sipser, the author proved that for endmarked context-free languages, the set of languages having a LR(k) grammar for a predefined $k \in \mathbb{N}$ ...
0
votes
1answer
46 views

Can I mix LL and LR parsing?

I want to go RD parsing with Shunting Yard for expression (for the sake of easier operator precedences and less left-recusion), is that considered no-good because nobody did that before?
3
votes
1answer
141 views

Is $\{a^nb^n\}\cup\{a^nb^{2n}\}$ LR(k)?

I was reading Knuth's paper "On The Translation of Languages from Left to Right", my particular interest being on RL($k$) languages (not a typo). By the end of the paper, he puts the grammar: $$ S \...
2
votes
1answer
3k views

Need for an augmented grammar

The question is under the concept of LR parser. Suppose the original grammar is S->AA A->aA|b Is it necessary to add an additional rule S'->S to make it as augmented grammar? In short, I want to ...
2
votes
0answers
326 views

How to find conflicts in LALR parser?

I have a LR analyser and I can't find out how to know whether the grammar is or is not LALR(1). I think that I have to merge states with the same rules. So I have to merge states: $2 - 12, 3 - 13, 4 -...
2
votes
0answers
27 views

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 ...
6
votes
0answers
70 views

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) parsing and ...
10
votes
2answers
584 views

How much bigger can an LR(1) automaton for a language be than the corresponding LR(0) automaton?

In an LR(0) parser, each state consists of a collection of LR(0) items, which are productions annotated with a position. In an LR(1) parser, each state consists of a collection of LR(1) items, which ...
0
votes
1answer
596 views

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 ...
12
votes
2answers
5k views

Is there any way to distinguish between LL(k) and LR(k) grammar?

I am recently studying about Compilers designing. I came to know about two types of grammar one is LL grammar and other is LR grammar. We also know the facts that every LL grammar is LR that is LL ...
4
votes
1answer
158 views

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 ...
4
votes
1answer
150 views

Are there automatic transformation of grammar algorithms?

From time to time you can write a grammar that creates shift/reduce conflict (for example) but after reading the grammar you notice that if you rewrite the productions the conflict will go away, ...
1
vote
0answers
24 views

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):...
0
votes
1answer
178 views

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 ...
1
vote
1answer
359 views

Is this grammar LR(1)?

A bit confused about whether this grammar is ambiguous or not C' -> C C -> d C u C C -> d C C -> ε I tried building the DFA for this but I get this ...
0
votes
1answer
171 views

How to create an LR($k$) grammar for a given language?

How can I construct an LR($k$) grammar (which $k$ is not really of interest for now) for a given language, say: $$L=\left\{w \in \{a, b\}^\star \ | \ \exists u \in \{a, b\}, v \in \{a, b\}^\star: w = ...