Syntax error recovery in parsing expression grammars

Medeiros, Sérgio; Mascarenhas, Fabio

doi:10.1145/3167132.3167261

Cited by 6 publications

(11 citation statements)

References 18 publications

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“…We have presented a mechanism for partially automating the process of adding error reporting and error recovery to parsers based on Parsing Expression Grammars. To achieve this, we proposed algorithms that automatically annotate the LL(1) parts of a PEG with error labels [2,3] and associates recovery expressions for these labels [4].…”

Section: Resultsmentioning

confidence: 99%

“…ANTLR automatically generates from a grammar description a parser with error reporting and recovery mechanisms, so the user does not need to annotate the grammar. After an error, ANTLR parses the entire input again to determine the error, which can lead to a poor performance when compared to our approach [4].…”

Section: Related Workmentioning

confidence: 97%

“…We can leverage the same labels to add an error recovery mechanism, by attaching a recovery expression to each label. This expression is just a regular parsing expression, and it usually skips the erroneous input until reaching a synchronization point, while producing a dummy AST node [4,5].…”

Section: Introductionmentioning

confidence: 99%

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Automatic syntax error reporting and recovery in parsing expression grammars

Medeiros

Alvez

Mascarenhas

2020

Science of Computer Programming

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Error recovery is an essential feature for a parser that should be plugged in Integrated Development Environments (IDEs), which must build Abstract Syntax Trees (ASTs) even for syntactically invalid programs in order to offer features such as automated refactoring and code completion.Parsing Expressions Grammars (PEGs) are a formalism that naturally describes recursive top-down parsers using a restricted form of backtracking. Labeled failures are a conservative extension of PEGs that adds an error reporting mechanism for PEG parsers, and these labels can also be associated with recovery expressions to provide an error recovery mechanism. These expressions can use the full expressivity of PEGs to recover from syntactic errors.Manually annotating a large grammar with labels and recovery expressions can be difficult. In this work, we present algorithms that automatically annotates a PEG with labels, and build their corresponding recovery expressions.We evaluate these algorithms by using them to generate error recovering parsers for four programming languages: Titan, Pascal, C and Java. The results show that with a small amount of manual intervention our approach can be used to produce error recovering parsers for PEGs where most choices have alternatives with disjoint F IRST sets.

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Section: Resultsmentioning

confidence: 99%

Section: Related Workmentioning

confidence: 97%

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Automatic syntax error reporting and recovery in parsing expression grammars

Medeiros

Alvez

Mascarenhas

2020

Science of Computer Programming

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“…al. [30] presented a parser expression grammar (PEG). While working on the structure of PEG's, authors also demonstrated some properties of context-free grammars (CFG) and PEG's.…”

Section: Literature Reviewmentioning

confidence: 99%

LL (1) Parser versus GNF inducted LL (1) Parser on Arithmetic Expressions Grammar: A Comparative Study

Ali

Naveed

Naseem

et al. 2020

QUESTRJ

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The prime objective of the proposed study is to determine the induction of Greibach Normal Form (GNF) in Arithmetic Expression Grammars to improve the processing speed of conventional LL(1) parser. Conventional arithmetic expression grammar and its equivalent LL(1) is used in the study which is converted. A transformation method is defined which converts the selected grammar into a Greibach normal form that is further converted into a GNF based parser through a method proposed in the study. These two parsers are analyzed by considering 399 cases of arithmetic expressions. During statistical analysis, the results are initially examined with the Kolmogorov-Smirnov and Shapiro-Wilk test. The statistical significance of the proposed method is evaluated with the Mann-Whitney U test. The study described that GNF based LL(1) parser for arithmetic take fewer steps than conventional LL(1) grammar. The ranks and asymptotic significance depict that the GNF based LL(1) method is significant than the conventional LL(1) approach. The study adds to the knowledge of parsers itself, parser expression grammars (PEG’s), LL(1) grammars, Greibach Normal Form (GNF) induced grammar structure, and the induction of Arithmetic PEG’s LL(1) to GNF based grammar.

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“…However, this first labeled failures formalization makes harder to recover from an error in its own context, since when a label is handled in a choice, the information about the error context is lost. Because of this, attempts to deal with error recovery in PEGs favored a semantics where the ⇑ operator itself handles the error [6,16]. To recover from an error, the ⇑ operator tries to match a recovery expression (a regular parsing expression).…”

Section: Related Workmentioning

confidence: 99%

A semantic framework for PEGs

Medeiros

Olarte

2020

Proceedings of the 13th ACM SIGPLAN International Conference on Software Language Engineering

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Parsing Expression Grammars (PEGs) are a recognition-based formalism which allows to describe the syntactical and the lexical elements of a language. The main difference between Context-Free Grammars (CFGs) and PEGs relies on the interpretation of the choice operator: while the CFGs' unordered choice | ′ is interpreted as the union of the languages recognized by and ′ , the PEGs' prioritized choice / ′ discards ′ if succeeds. Such subtle, but important difference, changes the language recognized and yields more efficient parsing algorithms. This paper proposes a rewriting logic semantics for PEGs. We start with a rewrite theory giving meaning to the usual constructs in PEGs. Later, we show that cuts, a mechanism for controlling backtracks in PEGs, finds also a natural representation in our framework. We generalize such mechanism, allowing for both local and global cuts with a precise, unified and formal semantics. Hence, our work strives at better understanding and controlling backtracks in parsers for PEGs. The semantics we propose is executable and, besides being a parser with modest efficiency, it can be used as a playground to test different optimization ideas. More importantly, it is a mathematical tool that can be used for different analyses.

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Syntax error recovery in parsing expression grammars

Cited by 6 publications

References 18 publications

Automatic syntax error reporting and recovery in parsing expression grammars

Automatic syntax error reporting and recovery in parsing expression grammars

LL (1) Parser versus GNF inducted LL (1) Parser on Arithmetic Expressions Grammar: A Comparative Study

A semantic framework for PEGs

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