From regexes to parsing expression grammars

Medeiros, Sérgio; Mascarenhas, Fabio; Ierusalimschy, Roberto

doi:10.1016/j.scico.2012.11.006

Cited by 19 publications

(14 citation statements)

References 10 publications

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“…Medeiros et al presented a formalization of regular expressions and PEGs, using the framework of natural semantics [10]. In this section, we present a formalization of PEGwUC, based on their work.…”

Section: Semanticsmentioning

confidence: 99%

“…A is a nonterminal and this is a placeholder for patterns of terminals in common with CFGs. Let a 10 be an input string. Then, intuitively, we consider the expression consumes a 10 .…”

Section: Introductionmentioning

confidence: 99%

“…Let a 10 be an input string. Then, intuitively, we consider the expression consumes a 10 . However, contrary to our intuition, the expression consumes a 4 .…”

Section: Introductionmentioning

confidence: 99%

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Parsing Expression Grammars with Unordered Choices

Chida

Kuramitsu

2017

Journal of Information Processing

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Abstract:Parsing expression grammars (PEGs) were formalized by Ford in 2004, and have several pragmatic operators (such as ordered choice and unlimited lookahead) for better expressing modern programming language syntax. In addition, PEGs can be parsed in a linear time by using recursive-descent parsing and memoization. In this way, PEGs have a lot of positive aspects. On the other hand, it is known that ordered choices defy intuition. They may cause bugs. This is due to a priority of an ordered choice. To avoid this, unordered choices are required. In this paper, we define a parsing expression grammar with unordered choices (PEGwUC), an extension of a PEG with unordered choices. By the extension, it is expected that a PEGwUC includes both a PEG and a context-free grammar (CFG), and this allows us to write a grammar more intuitively. Furthermore, we show an algorithm for parsing a PEGwUC. The algorithm runs in a linear time when a PEGwUC does not include unordered choice and in a cubic time in worst-case running time.

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Section: Semanticsmentioning

confidence: 99%

“…A is a nonterminal and this is a placeholder for patterns of terminals in common with CFGs. Let a 10 be an input string. Then, intuitively, we consider the expression consumes a 10 .…”

Section: Introductionmentioning

confidence: 99%

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Parsing Expression Grammars with Unordered Choices

Chida

Kuramitsu

2017

Journal of Information Processing

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“…Despite the differences, we can translate any regular expressions into an equivalent parsing expression using tricks described in Medeiros et al (2014). More importantly, DTDs, as described in Section 2, disallow non-deterministic regular expressions such as (a|ab)c and a * a, which behave differently in PEGs.…”

Section: Dtds Vs Pegsmentioning

confidence: 99%

XML schema validation using parsing expression grammars

Kuramitsu

Hamaguchi

2015

Preprint

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Schema validation is an integral part of reliable information exchange on the Web. However, implementing an efficient schema validation tool is not easy. We highlight the use of parsing expression grammars (PEGs), a recognition-based foundation for describing syntax, and apply it to the XML/DTD validation. This paper shows that structural schema constraints in document type definitions (DTDs) can be validated by the converted PEGs with the linear time and constant space consumption. We study the performance of several existing PEG-based tools, and then confirm that the converted PEGs achieve a practical and even competitive level of performance under existing standard XML/DTD validators.

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“…Our presentation of PEGs is slightly different from Ford's [3], and comes from earlier work [12,13]. This style makes the exposition of our extensions, and their Empty String Fig.…”

Section: Parsing Expression Grammars and Left Recursionmentioning

confidence: 99%

Left recursion in Parsing Expression Grammars

Medeiros¹,

Mascarenhas²,

Ierusalimschy³

2014

Science of Computer Programming

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Abstract. Parsing Expression Grammars (PEGs) are a formalism that can describe all deterministic context-free languages through a set of rules that specify a top-down parser for some language. PEGs are easy to use, and there are efficient implementations of PEG libraries in several programming languages. A frequently missed feature of PEGs is left recursion, which is commonly used in Context-Free Grammars (CFGs) to encode left-associative operations. We present a simple conservative extension to the semantics of PEGs that gives useful meaning to direct and indirect left-recursive rules, and show that our extensions make it easy to express left-recursive idioms from CFGs in PEGs, with similar results. We prove the conservativeness of these extensions, and also prove that they work with any left-recursive PEG.

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From regexes to parsing expression grammars

Cited by 19 publications

References 10 publications

Parsing Expression Grammars with Unordered Choices

Parsing Expression Grammars with Unordered Choices

XML schema validation using parsing expression grammars

Left recursion in Parsing Expression Grammars

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