What is the difference between LR, SLR, and LALR parsers?

Posted by equilibrium on Stack Overflow See other posts from Stack Overflow or by equilibrium
Published on 2010-04-20T14:55:52Z Indexed on 2010/04/20 15:23 UTC
Read the original article Hit count: 438

Filed under:

parsers

|

grammar

|

compiler

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?

And how to show whether a grammar is LR, SLR, or LALR? For an LL grammar we just have to show that any cell of the parsing table should not contain multiple production rules. Any similar rules for LALR, SLR, and LR?

For example, how can we show that the grammar

S --> Aa | bAc | dc | bda
A --> d

is LALR(1) but not SLR(1)?

© Stack Overflow or respective owner

Related posts about parsers

Trouble parsing quotes with SAX parser (javax.xml.parsers.SAXParser) on Android API 1.5

as seen on Stack Overflow - Search for 'Stack Overflow'
When using a SAX parser, parsing fails when there is a " in the node content. How can I resolve this? Do I need to convert all " characters? In other words, anytime I have a quote in a node: <node>characters in node containing "quotes"</node> That node gets butchered into multiple… >>> More
Trouble parsing quotes with SAX parser (javax.xml.parsers.SAXParser)

as seen on Stack Overflow - Search for 'Stack Overflow'
When using a SAX parser, parsing fails when there is a " in the node content. How can I resolve this? Do I need to convert all " characters? In other words, anytime I have a quote in a node: <node>characters in node containing "quotes"</node> That node gets butchered into multiple… >>> More
E: Sub-process /usr/bin/dpkg returned an error code (1) seems to be choking on kde-runtime-data version issue

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
12.04 LTS, on a dell mini 10. Install stable until about a week ago. Updated about 1x a week, sometimes more often. Several days ago, I booted up and the system was no longer working correctly. All these symptoms occurred simultaneously: Cannot run (exit on opening, every time): Update manager, software… >>> More
Text extraction with java html parsers

as seen on Stack Overflow - Search for 'Stack Overflow'
I want to use an html parser that does the following in a nice, elegant way Extract text (this is most important) Extract links, meta keywords Reconstruct original doc (optional but nice feature to have) From my investigation so far jericho seems to fit. Any other open source libraries you guys… >>> More
Source of parsers for programming languages?

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm dusting off an old project of mine which calculates a number of simple metrics about large software projects. One of the metrics is the length of files/classes/methods. Currently my code "guesses" where class/method boundaries are based on a very crude algorithm (traverse the file, maintaining… >>> More

Related posts about grammar

Convert The Context Free Grammar to LL1 Grammar

as seen on Stack Overflow - Search for 'Stack Overflow'
hi I want to write a program to gives grammar as input and change it to LL1. my problem is converting to LL1 I don't have any algorithm to convert. I earn grammar from some input text by a simple text analyzer but how I can change it to LL1 ? is there any algorithm that is clear to implement. >>> More
English Grammar Parsing in PHP (Link Grammar)

as seen on Stack Overflow - Search for 'Stack Overflow'
Is there anyway to use the Link Grammar or AbiSource grammar checker in PHP (or C# but I'd prefer php)? I need to have a tree structure for english sentences. Any ideas? The only things I found were in C and I can't use them on a shared host. >>> More
Good grammar for date data type for recursive descent parser LL(1)

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm building a custom expression parser and evaluator for production enviroment to provide a limited DSL to the users. The parser itself as the DSL, need to be simple. The parser is going to be built in an exotic language that doesn't support dynamic expression parsing nor has any parser generator… >>> More
Parsing a string, Grammar file.

as seen on Stack Overflow - Search for 'Stack Overflow'
How would I separate the below string into its parts. What I need to separate is each < Word including the angle brackets from the rest of the string. So in the below case I would end up with several strings 1. "I have to break up with you because " 2. "< reason " (without the spaces) 3. "… >>> More
Efficient Context-Free Grammar parser, preferably Python-friendly

as seen on Stack Overflow - Search for 'Stack Overflow'
I am in need of parsing a small subset of English for one of my project, described as a context-free grammar with (1-level) feature structures (example) and I need to do it efficiently . Right now I'm using NLTK's parser which produces the right output but is very slow. For my grammar of ~450 fairly… >>> More