Parsing for agile modeling

Agile modeling refers to a set of methods that allow for a quick initial development of an importer and its further refinement. These requirements are not met simultaneously by the current parsing technology. Problems with parsing became a bottleneck in our research of agile modeling. In this thesis we introduce a novel approach to specify and build parsers. Our approach allows for expressive, tolerant and composable parsers without sacrificing performance. The approach is based on a context-sensitive extension of parsing expression grammars that allows a grammar engineer to specify complex language restrictions. To insure high parsing performance we automatically analyze a grammar definition and choose different parsing strategies for different parts of the grammar. We show that context-sensitive parsing expression grammars allow for highly composable, tolerant and variable-grained parsers that can be easily refined. Different parsing strategies significantly insure high-performance of parsers without sacrificing expressiveness of the underlying grammars

Extending the BiYacc framework with ambiguous grammars

Dissertação de mestrado em Computer ScienceContrarily to most conventional programming languages where certain symbols are used so as to create non-ambiguous grammars, most recent programming languages allow ambiguity. This results in the necessity for a generic parser that can deal with this ambiguity without loss of performance. Currently, there is a GLR parser generator written in Haskell, integrated in the BiYacc system, developed by Departamento de Informática (DI), Universidade do Minho (UM), Portugal in collaboration with the National Institute of Informatics, Japan. In this thesis, this necessity for a generic parser is attacked by developing disambiguation filters for this system which improve its performance, as well as by implementing various known optimizations to this parser generator. Finally, performance tests are used to measure the results of the developed work.Contrariamente às linguagens de programação mais convencionais em que certos símbolos eram utilizados por forma a criar gramáticas não ambíguas, as linguagens mais recentes permitem ambiguidade, que por sua vez cria a necessidade de um parser genérico que consiga lidar com esta ambiguidade sem grandes perdas de performance. Atualmente, existe um gerador de parsers GLR em Haskell integrado no sistema BiYacc, desenvolvido pelo DI, UM, Portugal, em colaboração com o National Institute of Informatics, Japão. Nesta tese, são desenvolvidos filtros de desambiguidade para este sistema que aumentam a sua performance, assim como são feitas otimizações a vários níveis e se implementa um gerador de parsers usando um algoritmo GLL, que poderá trazer várias vantagens a nível de performance comparativamente com o algoritmo GLR atualmente implementado. Finalmente, são feitos testes de performance para avaliar os resultados do trabalho desenvolvido

InDubio: a combinator library to disambiguate ambiguous grammars

First Online: 29 September 2020To infer an abstract model from source code is one of the main tasks of most software quality analysis methods. Such abstract model is called Abstract Syntax Tree and the inference task is called parsing. A parser is usually generated from a grammar specification of a (programming) language and it converts source code of that language into said abstract tree representation. Then, several techniques traverse this tree to assess the quality of the code (for example by computing source code metrics), or by building new data structures (e.g, flow graphs) to perform further analysis (such as, code cloning, dead code, etc). Parsing is a well established technique. In recent years, however, modern languages are inherently ambiguous which can only be fully handled by ambiguous grammars. In this setting disambiguation rules, which are usually included as part of the grammar specification of the ambiguous language, need to be defined. This approach has a severe limitation: disambiguation rules are not first class citizens. Parser generators offer a small set of rules that can not be extended or changed. Thus, grammar writers are not able to manipulate nor define a new specific rule that the language he is considering requires. In this paper we present a tool, name InDubio, that consists of an extensible combinator library of disambiguation filters together with a generalized parser generator for ambiguous grammars. InDubio defines a set of basic disambiguation rules as abstract syntax tree filters that can be combined into more powerful rules. Moreover, the filters are independent of the parser generator and parsing technology, and consequently, they can be easily extended and manipulated. This paper presents InDubio in detail and also presents our first experimental results.- (undefined

Contributions to the Construction of Extensible Semantic Editors

This dissertation addresses the need for easier construction and extension of language tools. Specifically, the construction and extension of so-called semantic editors is considered, that is, editors providing semantic services for code comprehension and manipulation. Editors like these are typically found in state-of-the-art development environments, where they have been developed by hand. The list of programming languages available today is extensive and, with the lively creation of new programming languages and the evolution of old languages, it keeps growing. Many of these languages would benefit from proper tool support. Unfortunately, the development of a semantic editor can be a time-consuming and error-prone endeavor, and too large an effort for most language communities. Given the complex nature of programming, and the huge benefits of good tool support, this lack of tools is problematic. In this dissertation, an attempt is made at narrowing the gap between generative solutions and how state-of-the-art editors are constructed today. A generative alternative for construction of textual semantic editors is explored with focus on how to specify extensible semantic editor services. Specifically, this dissertation shows how semantic services can be specified using a semantic formalism called refer- ence attribute grammars (RAGs), and how these services can be made responsive enough for editing, and be provided also when the text in an editor is erroneous. Results presented in this dissertation have been found useful, both in industry and in academia, suggesting that the explored approach may help to reduce the effort of editor construction