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Topic: LR parser


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In the News (Sat 28 Nov 09)

  
  Canonical LR parser - Wikipedia, the free encyclopedia
A canonical LR parser or LR(1) parser is an LR parser whose parsing tables are constructed in a similar way as with LR(0) parsers except that the items in the item sets also contain a follow, i.e., a terminal that is expected by the parser after the right-hand side of the rule.
which would mean that the parser has read a string corresponding to B and expects next a string corresponding to C followed by the terminal 'a'.
LR(1) parsers can deal with a very large class of grammars but their parsing tables are often very big.
en.wikipedia.org /wiki/Canonical_LR_parser   (550 words)

  
 LR parser: Facts and details from Encyclopedia Topic   (Site not responding. Last check: 2007-09-17)
A compiler-compiler or parser generator is a utility for generating the source code of a parser, interpreter or compiler from an annotated language...
A simple lr parser or slr parser is an lr parser for which the parsing tables are generated as for an lr(0) parser except that it only performs a reduction...
A chart parser is a type of parser commonly used for natural languages that uses a data-driven approach based on a set of grammatical rules and a dictionary...
www.absoluteastronomy.com /encyclopedia/l/lr/lr_parser1.htm   (3486 words)

  
 Parser
A parser is a computer program or a component of a program that analyses the grammatical structure of an input, with respect to a given formal grammar.
Parsers can be made both for natural languages and for programming languages.
For example LALR parsers are capable of efficiently analysing a wide class of context free grammars.
www.ebroadcast.com.au /lookup/encyclopedia/pa/Parser.html   (254 words)

  
 LR parsing
A LR parser is a type of shift/reduce parser that does not use backtracking (it is the most general type of non-backtracking S/R parser currently known).
LR parsers also tend to produce larger tables than LL parsers.[1] The LR parser was first described by Knuth in 1965[2].
All LR parsers use the same algorithm; they differ in the way the table is generated.
www.logicalshift.demon.co.uk /unix/parse/lr.html   (502 words)

  
 PCYDB Manual
The generated parser starts with the input word of the program source code, which is internally recognized as a token and attempts to match a syntax structure for a string of tokens.
The parsing table is the key component of a LR parser because it determines the characteristics of the parser.
Since the parser uses the driver routine to consult the parsing table to switch between various states during the process of getting a token from input stream, setting a breakpoint at a particular state makes it possible to follow the execution of the parser and check the internal variables maintained by the parser.
www.abxsoft.com /pcydb.html   (5866 words)

  
 GOLD Parsing System - Glossary
LR parser generators, such as YACC and GOLD, construct these tables by analyzing the grammar and determining all the possible "states" the system can be in when parsing.
Lookahead parsers maintain a list of terminals which are expected to be read from each state, given that the syntax of the program is correct.
In the bottom-up parser engines, such as GOLD and YACC, a shift pushes the token onto an internal stack that is used to hold tokens that are being used to construct completed rules.
www.devincook.com /goldparser/articles/glossary.htm   (1088 words)

  
 About LALR Parsing
The primary goal a parser is to organize a sequence of tokens based on the rules of a formal language.
LR Parsing, or Left-to-right Right-derivation parsing, uses tables to determine when a rule is complete and when additional tokens must be read from the source string.
LR parser generators construct these tables by analyzing the grammar and determining all the possible "states" the system can have when parsing.
www.devincook.com /GOLDParser/doc/about/lalr.htm   (697 words)

  
 ML-Yacc User's Manual Version 2.3
The symbol names and types are used to construct a datatype union for the values on the semantic stack in the LR parser and to name the values associated with subcomponents of a rule.
You may want each invocation of the entire parser to be parameterized by a particular argument, such as the file-name of the input being parsed in an invocation of the parser.
Two possibilities are turning the lexer and parser structures into closed functors, that is, functors which do not refer to types or values defined outside their body or outside their parameter structures (except for pervasive types and values), and creating a functor which encapsulates the code necessary to invoke the parser.
www.cs.princeton.edu /~appel/modern/ml/ml-yacc/manual.html   (6254 words)

  
 Introduction   (Site not responding. Last check: 2007-09-17)
A parser tries to recover from a syntax error by making a single token insertion, deletion, or substitution near the point in the input stream at which the error was detected.
ML-Yacc uses the ML modules facility to specify the interface between a parser that it generates and a lexical analyzer that must be supplied by you.
The error-correcting LR parser implements the algorithm by keeping a queue of its state stacks before shifting tokens and using a lazy stream for the lexer.
www.smlnj.org /doc/ML-Yacc/mlyacc001.html   (1419 words)

  
 Elkhound and Elsa
Its high performance is a result of a novel combination of GLR and LR parsing, wherein the parser decides on a token-by-token basis which algorithm to use.
JBP, the Java Boolean Parser, is a parser generator for Java (the generated parser is Java source code) written in Java.
Accent is parser generator based on a combination of the Earley and LL parsing algorithms.
www.cs.berkeley.edu /~smcpeak/elkhound   (3023 words)

  
 Glossary of Parsing Terms
A parser is a program, or more likely a procedure within a program, which scans a sequence of input characters or input tokens and accumulates them in an input buffer or stack as determined by a set of productions which constitute a grammar.
A parser generator, such as AnaGram, is a program that converts a grammar, a rule-based description of the input to a program, into a conventional, procedural module called a parser.
The tokens identified by a parser are concrete instances of the abstract tokens in the grammar.
www.parsifalsoft.com /gloss.html   (7372 words)

  
 LL and LR Translator Need k   (Site not responding. Last check: 2007-09-17)
A translator consists of a syntactic parser or recognizer augmented with semantic actions that are triggered by the recognizer.
Both LR or LL parsers use a finite state machine; their recognition strength is a function of (i) the amount of context} and (ii) the amount of lookahead.
Finally, we know of a LR(k) parser generator [Grosch95] that uses a variant of LR (k) that is nearing completion.
www.antlr.org /Articles/needlook.html   (3437 words)

  
 Relation to probabilistic LR parsing
Generalized LR parsing is an extension that allows parallel tracking of multiple state transitions and stack actions by using a graph-structured stack [Tomita1986].
Even though an Earley parser runs with the same linear time and space complexity as an LR parser on grammars of the appropriate LR class, the constant factors involved will be much in favor of the LR parser as almost all the work has already been compiled into its transition and action table.
However, the size of LR parser tables can be exponential in the size of the grammar (due to the number of potential item subsets).
www.icsi.berkeley.edu /~stolcke/papers/cl95/node43.html   (785 words)

  
 Bottom Up Parsing   (Site not responding. Last check: 2007-09-17)
Notice that the configuration of the parser corresponds to a reverse rightmost derivation.
An LR(k) parser's recognition strength lies with the fact that a given parser state may correspond to multiple grammar positions.
Increasing the amount of lookahead beyond k=1 for both LL and LR parsers is useful.
www.cs.usfca.edu /~parrt/course/652/lectures/LR.parsing.html   (1273 words)

  
 Essence---An LR Parser Generator for Scheme -- Running a Parser   (Site not responding. Last check: 2007-09-17)
Parsing with respect to a grammar does not require generating a specialized parser along with the associated overhead of compiling and loading.
Essence provides general parsers which accept a grammar as input and parse "right away." This allows incremental debugging and development of attributed grammars to be used with Essence.
Lookahead is a non-negative integer denoting the lookahead the parser uses.
www.informatik.uni-freiburg.de /proglang/software/essence/doc/html/essence_4.html   (211 words)

  
 Romanian Language Technology   (Site not responding. Last check: 2007-09-17)
In this section we will first have a look at how the standard LR parsing algorithm was extended to efficiently handle the non determinism occurring due to the conflicting entries in the LR parsing table and then, in the fourth section, we will show how the algorithm was modified for unification-based grammars.
A LR Parser consists of a control program which is the same for all grammars, and a parse table with two components: ACTION and GOTO.
A LR parser configuration is a pair (s0 X1 s1 X2 s2 … Xm sm, ai ai+1 … an $) with the first component being the stack contents and the second the remaining input.
www.racai.ro /books/awde/ciocoiu1.html   (338 words)

  
 Essence, an LR parser generator for Scheme   (Site not responding. Last check: 2007-09-17)
The generated parsers perform error recovery, and are highly efficient.
Rather, the parser generator results from a general parser which takes the input grammar as a parameter; no generation and recompilation is necessary to try out changes to a grammar.
The generated parsers result from the general parser by an automatic program transformation called partial evaluation.
www.informatik.uni-freiburg.de /proglang/software/essence   (106 words)

  
 SGLR
The SGLR parser interprets parse tables generated by the ParsetableGenerator from an SDF2 syntax definition.
The parser outputs parse trees or parse forests.
The effect is that an SGLR parser does not complain about conflicts in the parse table.
www.cwi.nl /htbin/sen1/twiki/bin/view/SEN1/SGLR   (145 words)

  
 Parsing FORTRAN   (Site not responding. Last check: 2007-09-17)
In the parser, tokens that are associated with a lexical value are immediately reduced to store the value.
Since Bison is an LR parser, linked lists are built in reverse, and must be switched for inorder traversal.
The switching is done before sublists are attached to the main part of the program, and for the main program, directly after the final grammar reduction before the code generation routines are invoked.
icl.cs.utk.edu /projects/f2j/f2jreport/node24.html   (507 words)

  
 Geneseo CSci 331 Parser Assignment   (Site not responding. Last check: 2007-09-17)
This assignment is intended to consolidate your understanding of LR parsing.
Note that you have a big start on this parser from Assignment 3, in which you built the SLR states from which your parse tables will come.
I have provided source and object code in Java for a number of support classes for this parser -- e.g., classes that represent all the syntax tree nodes required by MinimL, interfaces for parsers in general, etc. The relevant files are on the CS Suns, in directory ~baldwin/csci331/classes.
www.cs.geneseo.edu /~baldwin/csci331/spring2002/hw-parser.html   (359 words)

  
 Context-Free Grammars and Parser Automata   (Site not responding. Last check: 2007-09-17)
Unlike most other parser generation systems, this library attempts to maximize generation speed so that the parser can be generated dynamically, making it easier for grammar definitions to be completely integrated into the surrounding program (as with the system described in and).
Encapsulates the finite-state automaton portion of a parser for a context-free grammar.
An LR (bottom-up) parser is, as we mentioned earlier, a pushdown automaton.
monday.sourceforge.net /lib/language/grammar/grammar.html   (9654 words)

  
 How to write a Parser / translator using Lex /Yacc
A Parser for a Grammar is a program which takes in the Language string as it's input and produces either a corresponding Parse tree or an Error.
The LR means Left-to- Right signifying the parser which reads the input string from left to right.
It differs from LR in the fact that it will look ahead one symbol in the input string before going for a reduce action.
members.tripod.com /~ashimg/Parser.html   (2352 words)

  
 LR Parsing
Based on the contents of the stack and the lookahead the parser performs two kinds of actions.
Initially the stack is empty and the parser is at the beginning of the input.
The parser excepts the input when the stack is empty and the end-of-file marker $ is the input.
cs.wwc.edu /~aabyan/464/BUP.html   (296 words)

  
 LR0_Grammar (Generic Interpreter 1.0 Private API)
LR(0) parsing is not very practical, since it ignores lookahead information and is easily confused, but it forms a basis around which SLR(1) and LR(1) parsers are constructed.
The parse trees through which this parser transitions.
Interprets a source character stream by LR shift-reduce ascent.
www.csupomona.edu /~carich/gi/gi-1.0/docs/private/gi/LR0_Grammar.html   (192 words)

  
 Geneseo CSci 331 Implementing LR Parsers 1   (Site not responding. Last check: 2007-09-17)
Observation 2: All LR parsers work in the same basic manner, i.e.,
But each LR parser differs in the contents of its parse tables, and in details of reductions (since they depend on the grammar the parser parses)
So want to separate the general features of LR parsers from the language-specific features of specific ones, so the general features can be reused:
www.cs.geneseo.edu /~baldwin/csci331/spring2002/lrimpl0311.html   (139 words)

  
 [No title]
Ans: 1) By constructing a DFA that encodes all parser states, and transitions on terminals and nonterminals.
The transitions on terminals are the parser actions(also called the action table) and transitions on nonterminals resulting in a new state (also called the goto table).
LR(0) parser (like a FSA) needs to know how much the production (on the rhs) we have scanned so far.
www.cs.rpi.edu /~moorthy/Courses/compiler98/Lectures/lecturesinppt/lecture7.ppt   (263 words)

  
 [No title]   (Site not responding. Last check: 2007-09-17)
The # LR parser itself is defined in terms of an object (which allows multiple # parsers to co-exist).
Users shouldn't # notice unless they are trying to define multiple parsers at the same # time using threads (in which case they should have their head examined).
These are not # used during table construction and are independent of the actual LR # table generation algorithm #----------------------------------------------------------------------------- # This class is used to hold non-terminal grammar symbols during parsing.
www-personal.engin.umich.edu /~dhildebz/591/pynfs/yacc.py   (2152 words)

  
 SDF / Generalized LR
A parsing algorithm that maintains multiple LR parsing states in parallel.
PyGgy A Python parser generator that generates SLR tables for a GLR parsing engine.
The maintainers of Elkhound maintain a list of implementations as well.
www.program-transformation.org /Sdf/GeneralizedLR   (116 words)

  
 Help with LR parser algorithm
The code should use the parse tables and determine wheather a word is accepted using the grammar provided and using the Parser tables.
We show how LR parsers for the analysis of arbitrary context-free grammars can be derived from classical Earley's parsing algorithm.
The result is a Generalized LR parsing algorithm working at complexity O(n3) in the worst case, which is achieved by the use of dynamic programming to represent the non-deterministic evolution of the stack instead of graph-structured stack representations, as has often been the case in previous approaches.
www.daniweb.com /techtalkforums/post22163.html#post22163   (377 words)

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