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Topic: Packrat parser

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	Parsing - TvWiki, the free encyclopedia (Site not responding. Last check: 2007-10-14)
		Generally, parsers operate in two stages, first identifying the meaningful tokens in the input, and then building a parse tree from those tokens.
		Parsers for programming languages tend to be based on context-free grammars because fast and efficient parsers can be written for them.
		Parsers are usually not written by hand but are generated by parser generators.
	www.tvwiki.tv /wiki/Parser (814 words)

	xml parser - parser
		Thus, it is a common strategy to create a relaxed parser for a context-free grammar which accepts a superset of the desired language constructs (that is, it accepts some invalid constructs); later, the unwanted constructs can be filtered out.
		The parser would contain rules to tell it that the characters , +, ^, (and) mark the start of a new token, so meaningless email cvar parser* parser tokens like "12*" or "(3" will not be generated.
		In the case of a calculator, the action javascript html parser is to evaluate the expression; a compiler, on the other hand, would generate the machine language that performs the functionality stated in the code.
	www.infotechloco.com /Inf-Computer-Topics-N---Q/Parser.html (884 words)

	Wikinfo \| 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, a process known as parsing.
		For example LALR parsers are capable of efficiently analysing a wide class of context free grammars.
		A parser can do this in essentially two ways: it can start with the input and attempt to rewrite it to the start symbol, a so-called bottom-up parser, or it can start with the start symbol and try to rewrite it to the input, a so-called top-down parser.
	www.wikinfo.org /wiki.php?title=Parser (326 words)

	Recursive descent parser Summary
		This particular type of parser, a recursive descent parser, uses recursive procedures to model the parse tree that is to be constructed that is it is an algorithm that calls itself within some part of executing its own task.
		A recursive descent parser is a top-down parser built from a set of mutually-recursive procedures (or a non-recursive equivalent) where each such procedure usually implements one of the production rules of the grammar.
		A packrat parser is a modification of recursive descent with backup that avoids nontermination by remembering its choices, so as not to make exactly the same choice twice.
	www.bookrags.com /Recursive_descent_parser (1052 words)

	Question: Graceful error recovery during parsing \| Lambda the Ultimate
		I was hoping for a few pointers to good information on parsers that can recover from errors and continue to parse the remainder of their input, skipping portions of the text that are not valid in a clean way.
		Packrat is definitely my favorite of the three from an ease of rule development standpoint.
		Just so everyone knows, I'm thinking about this parser in the context of a syntax-aware text editor, where the format of the language being edited could be described by attaching properties to text based on a grammar description written by the user...
	lambda-the-ultimate.org /node/view/1018 (1873 words)

	packrat - SWiK
		Packrat Parsing: a Practical Linear-Time Algorithm with Backtracking
		Text.Parsers.Frisby: a linear-time, composable parser for PEG grammars
		haskell parsing packrat PEG frisby … Aug 29
	swik.net /packrat (359 words)

	Packrat Parsing: Simple, Powerful, Lazy, Linear Time (Site not responding. Last check: 2007-10-14)
		Packrat parsing is a novel technique for implementing parsers in a lazy functional programming language.
		A packrat parser provides the power and flexibility of top-down parsing with backtracking and unlimited lookahead, but nevertheless guarantees linear parse time.
		Yet despite its power, packrat parsing shares the same simplicity and elegance as recursive descent parsing; in fact converting a backtracking recursive descent parser into a linear-time packrat parser often involves only a fairly straightforward structural change.
	pdos.csail.mit.edu /~baford/packrat/icfp02 (344 words)

	Text.Parsers.Frisby
		frisby parsers achieve composability by having a compilation pass, recursive parsers are specified using the recursive do notation 'mdo' which builds up a description of your parser where the recursive calls for which memoized entries must be made are explicit.
		These are how a frisby parser decides what path to take, whereas a backtracking parser might try a path, then backtrack if it got it wrong, a frisby parser can look at all possible paths before deciding which one to take via these predicates.
		packrat parsers have no past, but can 'see' arbitrarily far into all of its potential futures, traditional monadic parsers can accumulate a history, but cannot see more than a token or two into the future, and evaluating multiple futures to any degree imposes a significant run-time penalty due to backtracking.
	repetae.net /computer/frisby (1357 words)

	Packrat Parsing and Parsing Expression Grammars
		ANTLR, a well-established parser generator by Terence Parr, now in version 3 supports extensive PEG features and combines packrat parsing with LL parsing techniques.
		Frisby by John Meacham is a monadic packrat parser library for Haskell that uses advanced Haskell type system features to support dynamic specification of composable parsers.
		Pappy by Bryan Ford is a simple prototype packrat parser generator for Haskell.
	pdos.csail.mit.edu /~baford/packrat (471 words)

	Roman Redziejowski Publications
		Parsing Expression Grammar as a primitive recursive-descent parser with backtracking
		Packrat parsing is a general method to handle backtracking in recursive-descent parsers.
		The resulting primitive parser shows an acceptable behavior, indicating that packrat parsing might be an overkill for practical languages.
	home.swipnet.se /redz/roman/pubs.htm (743 words)

	Parsing Summary
		A parser is a program that enables the translation of source code, which is the original form of program instruction, into object code, or language that the computer is able to understand.
		Parsers are available for all standard programming languages, such as XML, Perl and Java.
		While the parser is the program that dissects the information, the compiler is essentially the language that specifies the way parsing is accomplished.
	www.bookrags.com /Parsing (2038 words)

	Parsing - CompWisdom
		A parser is an algorithm that determines whether a given input string is in a language and, as a side-effect, usually produces a parse tree for the input.
		The primary disadvantage of packrat parsing is its storage cost, which is a constant multiple of the total input size rather than being proportional to the nesting depth of the syntactic constructs appearing in the input.
		Packrat parsing is an adaptation of a 30-year-old tabular parsing algorithm that was never put into practice until now.
	www.compwisdom.com /topics/Parsing (3494 words)

	Gmane -- Mail To News And Back Again
		Frisby is an implementation of the 'packrat' parsing algorithm, which parse PEG grammars and have a number of very useful qualities, they are a generalization of regexes in a sense that can parse everything in LL(k), LR(k), and more, including things that require unlimited lookahead, all in guarenteed linear time.
		There is no need for a separate lexing pass when using a packrat parser due to the subsumpion of regular expressions, and the unlimited lookahead obviating the need to tokenize the input.
		Although the basic mechanism works, the API is still in flux, at the moment, parsers are specified almost exactly in their native grammar form.
	article.gmane.org /gmane.comp.lang.haskell.general/14128 (332 words)

	Packrat parser - Wikipedia, the free encyclopedia
		It has been suggested that this article or section be merged into parsing expression grammar.
		is a form of parser similar to a recursive descent parser in construction, except that during the parsing process it memoizes the intermediate results of all invocations of the mutually recursive parsing functions.
		Because of this memoization, a packrat parser has the ability to parse many context-free grammars and any parsing expression grammar (including some that do not represent context-free languages) in linear time.
	en.wikipedia.org /wiki/Packrat_parser (147 words)

	jmuk's blog \| The Haskell Sequence
		The parser combinator library that does this is a challengeable task -- but, here I applies a small approach to parse bencode format.
		In parser context, `a stream' corresponds to the parsed result, and the computed value to rest of text.
		With Packrat Parsing, we must define dvChar -- a function to calculate the `next' character of a stream -- by ourselves, so it is easier to use with ByteString.
	sequence.complete.org /blog/111 (1666 words)

	Squirrel
		Squirrel is a simple packrat parser implemented in Java 5.0.
		The parser is built by calling methods of the Squirrel class; no parser generation step is necessary.
		The only way to use the parser is to generate a parse tree for an entire input string, followed by walking the tree to generate any additional data structure needed.
	ozark.hendrix.edu /~ferrer/software/squirrel (353 words)

	Packrat Parsing: a Practical Linear-Time Algorithm with Backtracking - Ford (ResearchIndex) (Site not responding. Last check: 2007-10-14)
		Abstract: Packrat parsing is a novel and practical method for implementing linear-time parsers for grammars defined in Top-Down Parsing Language (TDPL).
		While TDPL was originally created as a formal model for top-down parsers with backtracking capability, this thesis extends TDPL into a powerful general-purpose notation for describing language syntax, providing a compelling alternative to traditional context-free grammars (CFGs).
		5.3 Space Consumption Probably the most striking characteristic of a packrat parser is the fact that it literally squirrels away...
	citeseer.ist.psu.edu /ford02packrat.html (635 words)

	LtU Classic Archives
		Packrat parsing is a novel and practical method for implementing linear-time parsers for grammars defined in Top-Down Parsing Language (TDPL).
		A packrat parser implemented in this way is almost identical in style and structure to a conventional recursive-descent parser with backtracking: the packrat parser essentially just uses a different method to "tie up" the mutually recursive calls that are made between the functions comprising the parser...
		Furthermore, whereas the expansions expressed in a CFG represent operations on whole strings, the reductions expressed in a TDPL grammar represent operations on prefixes of an input string.
	lambda-the-ultimate.org /classic/message11167.html (395 words)

	Tin Can Camera: 2006-05
		The Triep stuff is a combination of Trie with predicates that was another idea for incremental parsing taylored for interactive development.
		I'm going to add some form of trie to the parse states for autocompletion, though I may go back to using a standard trie as the calculus for the predicates is tricky, and reusing the packrat grammar may mean it's not needed.
		It's also true that both CLCE and ACE have been used to create running code for systems specified in natural language, but in my experience there are always problems with general purpose code generators (not that I'm saying anything of the quality of those projects in particular).
	www.tincancamera.com /blog/archive/2006_05_01_archive.html (717 words)

	Redesigning Spirit
		Yet, when the time came to add attributes to the parser framework, it was done rather in an ad-hoc manner, with the goal being 100% backward compatible with classic Spirit.
		The interesting realization is that the code size of exhaustive spirit rivals that of the hand coded parser (hand_coded.cpp), which is smaller than greedy spirit, most probably because there is no need for the difference parser to control the kleene star's greed.
		A parser will have to compute this information even if, in the end, they'll be thrown out anyway when we are not concerned with tree building.
	spirit.sourceforge.net /dl_docs/redesigning_spirit.html (3030 words)

	Encyclopedia (Site not responding. Last check: 2007-10-14)
		Typically, a parser transforms some input text into a data structure that can be processed easily, e.g.
		Such a data structure usually captures the implied hierarchy of the input and forms a tree or even a graph.
		Thus, a common strategy to accept such language constructs is to relax the parser, i.e.
	simple.seowaste.com /parser (490 words)

	Parsing (Site not responding. Last check: 2007-10-14)
		This term alludes to the pyparsing parsing monadic parsing packrat parser is parsing supplied.
		Bryan ford, packrat parsers are indicated by john meacham is a
		The papers are parsers parsing for analyzing cfgs for ambiguity.
	parsing.rainbowhungary.com (2616 words)

	Compilers@di.um.pt
		More practically, a parser is the part of a compiler that goes through a program and cuts it into identifiable chunks before translation.
		Also, we can say that a parser is an algorithm or program to determine the syntactic structure of a sentence or string of symbols in some language.
		A parser normally takes as input a sequence of tokens output by a lexical analyser and the grammar that defines language under consideration.
	www.di.uminho.pt /~gepl/LP/ConceptsP.html (288 words)

	Recursive Descent Parser for Ruby
		Just before writing this post I decided to Google that name, and lo and behold the first result is a Ruby recursive descent parser called RDParse, created by Dennis Ranke, that I posted to Code Snippets for posterity several months ago.
		Since both of these libraries are unlikely to be used at once and that Dennis doesn't seem to be maintaining his version, I've decided to stick with RDParse as the name of mine for now.
		One Response to “Recursive Descent Parser for Ruby”
	www.rubyinside.com /recursive-descent-parser-for-ruby-300.html (462 words)

	Re: Lazy evaluation (Site not responding. Last check: 2007-10-14)
		I > did a packrat parser some time back but it was more like "memoize for > later"; maybe I didn't read the packrat papers enough...
		From my reading of the papers he presents it > in a lazy framework but you can unroll the laziness by memoization of > the partial results of a recursive decent parser.
		I know your Rockit parser, but I've admit that I didn't tried it too much as it seems to be a bit outdated.
	blade.nagaokaut.ac.jp /cgi-bin/scat.rb/ruby/ruby-talk/99145 (277 words)

	Knowing.NET - Friday, 13 October 2006 (Site not responding. Last check: 2007-10-14)
		Packrat parsing evolves from a top-down predictive (aka recursive-descent) parser.
		The knock on recursive-descent parsing is that when an ambiguity is resolved, you have to backtrack up "what you've got" until you find an alternative and then you have to reparse the expression from that point forward.
		So anyway, if you read the paper, you'll see that the core of Packrat parsing is to change "what's remaining" from a string to a doubly-recursive data structure that represents "the remaining string, plus partial results of all previous attempts at disambiguation." The paper explains it very well, moving along in Haskell.
	www.knowing.net /default,date,2006-10-13.aspx (3550 words)

	Parsing - Wikipedia, the free encyclopedia
		For the computer programming language, see Parser (programming language).
		In computer science, parsing is the process of analyzing a sequence of tokens in order to determine its grammatical structure with respect to a given formal grammar.
		Parsing is also an earlier term for the diagraming of sentences in grammar of natural language, and is still used to diagram the grammar of inflected languages, such as the Romance languages or Latin.
	en.wikipedia.org /wiki/Parser (1256 words)

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