lr-grammar Questions
7
Solved
What advantages do LL parsers have over LR parsers to warrant their relative popularity in today's parser generator tools?
According to Wikipedia, LR parsing appears to have advantages over LL:
...
Greybeard asked 3/11, 2010 at 22:36
1
Solved
At many places (for example in this answer here), I have seen it is written that an LR(0) grammar cannot contain ε productions.
Also in Wikipedia I have seen statements like: An ε free LL(1) gramma...
Pajamas asked 16/1, 2022 at 14:50
1
Solved
I'm parsing a language that doesn't have statement terminators like ;. Expressions are defined as the longest sequence of tokens, so 5-5 has to be parsed as a subtraction, not as two statements (li...
Sanyu asked 3/1, 2022 at 20:56
4
Solved
I am working on my compilers concepts however I am a little confused...
Googling got me nowhere to a definite answer.
Is SLR and LR(0) parsers one and same? If not, whats the difference?
Royceroyd asked 11/9, 2011 at 12:59
9
Solved
What is the actual difference between LR, SLR, and LALR parsers? I know that SLR and LALR are types of LR parsers, but what is the actual difference as far as their parsing tables are concerned?
A...
Collen asked 20/4, 2010 at 14:55
7
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I know the basic differences of LL vs LR parsers. I also know that GLR, SLR, and LALR are all extensions of LR parsers. So my question in more details is...
Given a LL(*) parser and any variation ...
Tedmann asked 29/3, 2011 at 2:30
1
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I'm familiar with LR(1) parsers, which are usually taught in traditional compilers courses. I know that LR(2) parsers exist, but I've never seen one constructed before.
How is an LR(2) parser cons...
Defray asked 28/5, 2020 at 21:48
4
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Is there a good resource online with a collection of grammars for some of the major parsing algorithms (LL(1), LR(1), LR(0), LALR(1))? I've found many individual grammars that fall into these famil...
Wye asked 25/6, 2011 at 21:26
4
Can anyone give me a simple example of LL parsing versus LR parsing?
Wendall asked 12/5, 2011 at 9:8
4
I have the following grammar, which I'm told is LR(1) but not SLR(1):
S ::= a A | b A c | d c | b d a
A ::= d
I don't understand why this is. How would you prove this?
Wray asked 8/5, 2012 at 20:7
5
Solved
How do you identify whether a grammar is LL(1), LR(0), or SLR(1)?
Can anyone please explain it using this example, or any other example?
X → Yz | a
Y → bZ | ε
Z → ε
Scorpaenid asked 13/12, 2011 at 21:47
0
I have a grammar that, depending on the order of productions, happy reports 3 reduce/reduce conflicts or none. The minimal example I can find is:
%tokentype {Token}
%token
int { Int }
'-' { Neg ...
Haversine asked 5/3, 2018 at 22:33
2
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Historically, LALR(1) parsers were preferred over LR(1) parsers because of resource requirements required by the large number of states generated by LR(1) parsers. It's hard to believe that this co...
Livvie asked 11/6, 2014 at 23:54
3
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I understand both LR and LALR are bottom-up parsing algorithms, but what's the difference between the two?
What's the difference between LR(0), LALR(1), and LR(1) parsing? How can I tell if ...
Personable asked 29/10, 2013 at 16:9
1
Solved
I'm really struggling to unterstand the relationship between:
LR(0)
LL(0)
LALR(1)
SLR(1)
LR(1)
LL(1)
I'm pretty sure LALR(1) and SLR(1) are subsets of LR(1), but I'm lost about the others. Are...
Tenenbaum asked 15/4, 2016 at 16:19
1
I know that every LL(1) is also an LR(1). But what about the relationship between LL(1) and LR(0), can a LL(1) be a LR(0) as well?
Unplaced asked 10/1, 2016 at 15:53
4
Solved
I have trouble understanding how to compute the lookaheads for the LR(1)-items.
Lets say that I have this grammar:
S -> AB
A -> aAb | a
B -> d
A LR(1)-item is an LR(0) item with a look...
Airdrome asked 31/12, 2012 at 15:12
1
Solved
An LL(1)-parser needs a lookahead-symbol for being able to decide which production to use. This is the reason why I always thought the term "lookahead" is used, when a parser looks at the next inpu...
Sender asked 14/3, 2015 at 13:35
2
Solved
Can a LR(1) parser parse a grammar of this type?
S -> SA | A
A -> aSb | ab
I'm trying to write a Java program that implements this type of parser, but I only get the right results on a gra...
Bales asked 30/1, 2014 at 16:25
1
Solved
I'm trying to implement Warshall's algorithm to quickly compute LR(1) closures.
I think I understand how it works for LR(0):
The nodes of the graph are LR items, like A → B • C
The edges are "tr...
Albrecht asked 8/6, 2013 at 18:28
2
Solved
I'm experimenting with parsing on my free time, and I wanted to implement a shift-reduce parser for a very very simple grammar. I've read many online articles but I'm still confused on how to creat...
Anticlimax asked 11/1, 2014 at 16:12
1
Solved
I am confused by the following quote from Wikipedia:
In other words, if a language was reasonable enough to allow an
efficient one-pass parser, it could be described by an LR(k) grammar.
And t...
Disrate asked 19/12, 2013 at 14:1
1
Solved
Making artificial LR(k) grammars for k > 1 is easy:
Input: A1 B x
Input: A2 B y (introduce reduce-reduce conflict for terminal a)
A1 : a
A2 : a
B : b b b ... b (terminal b occurs k-1 times)
Howe...
Discriminate asked 26/11, 2013 at 2:18
2
Solved
Where can I find a simple (as much as possible, but no simpler!) implementation of an LR(1) parser generator?
I'm not looking for performance, just the ability to generate the LR(1) states (item s...
Covenantor asked 10/1, 2013 at 7:30
1
Solved
I've been reading on both in Wikipedia, and noticed that although LR(0) parsers exist, there's no such thing as LL(0) parser.
From what I read, I understand that the k in LL(k)/LR(k) means how man...
Staid asked 3/2, 2013 at 17:4
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