Abstract. Generalized LL (GLL) parsing is an extension of recursivedescent (RD) parsing that supports all context-free grammars in cubic time and space. GLL parsers have the direct relationship with the grammar that RD parsers have, and therefore, compared to GLR, are easier to understand, debug, and extend. This makes GLL parsing attractive for parsing programming languages. In this paper we propose a more e cient Graph-Structured Stack (GSS) for GLL parsing that leads to significant performance improvement. We also discuss a number of optimizations that further improve the performance of GLL. Finally, for practical scannerless parsing of programming languages, we show how common lexical disambiguation filters can be integrated in GLL parsing. Our new formulation of GLL parsing is implemented as part of the Iguana parsing framework. We evaluate the e↵ectiveness of our approach using a highly-ambiguous grammar and grammars of real programming languages. Our results, compared to the original GLL, show a speedup factor of 10 on the highly-ambiguous grammar, and a speedup factor of 1.5, 1.7, and 5.2 on the grammars of Java, C#, and OCaml, respectively.

Despite the long history of research in parsing, constructing parsers for real programming languages remains a difficult and painful task. In the last decades, different parser generators emerged to allow the construction of parsers from a BNF-like specification. However, still today, many parsers are handwritten, or are only partly generated, and include various hacks to deal with different peculiarities in programming languages. The main problem is that current declarative syntax definition techniques are based on pure contextfree grammars, while many constructs found in programming languages require context information.In this paper we propose a parsing framework that embraces context information in its core. Our framework is based on data-dependent grammars, which extend contextfree grammars with arbitrary computation, variable binding and constraints. We present an implementation of our framework on top of the Generalized LL (GLL) parsing algorithm, and show how common idioms in syntax of programming languages such as (1) lexical disambiguation filters, (2) operator precedence, (3) indentation-sensitive rules, and (4) conditional preprocessor directives can be mapped to datadependent grammars. We demonstrate the initial experience with our framework, by parsing more than 20 000 Java, C#, Haskell, and OCaml source files.

A revolution in utilities domain is underway, namely the Internet of Energy. Networked Embedded Devices (NEDs) are making the electricity grid itself, the homes and the factories smarter, increasing the possibilities of collaboration among them. It is expected that NEDs will offer their functionality as one or more services, one of which will be a real-time measurement of the energy they consume or produce. In such highly distributed heterogeneous infrastructures it is clear that the metering goes beyond the classical understanding; it is becoming ubiquitous, distributed and will be the core for future value added services. Modeling such dynamic event-based systems is a challenging approach. We focus our work on simulating large scale infrastructures where multiple web-service enabled devices offer metering data on an event based mode and provide some metrics for evaluating them.

The integration of database and programming languages is difficult due to the different data models and type systems prevalent in each field. We present a solution where the developer may express queries encompassing program and database data. The notation used for queries is based on comprehensions, a declarative style that does not impose any specific execution strategy. In our approach, the type safety of languageintegrated queries is analyzed at compile-time, followed by a translation that optimizes for database evaluation. We show the translation total and semantics preserving, and introduce a language-independent classification. According to this classification, our approach compares favorably with Microsoft's LINQ, today's best-known representative. We provide an implementation in terms of Scala compiler plugins, accepting two notations for queries: LINQ and the native Scala syntax for comprehensions. The prototype relies on Ferry, a query language that already supports comprehensions yet targets SQL:1999. The reported techniques pave the way for further progress in bridging the programming and the database worlds.

Constructing parsers based on declarative specification of operator precedence is a very old research topic, and there are various existing approaches. However, these approaches are either tied to a particular parsing technique, or cannot deal with all corner cases found in programming languages. In this paper we present an implementation of declarative specification of operator precedence for general parsing that (1) is independent of the underlying parsing algorithm, (2) does not require any grammar transformation that increases the size of the grammar, (3) preserves the shape of parse trees of the original, natural grammar, and (4) can deal with intricate cases of operator precedence found in functional programming languages such as OCaml. Our new approach to operator precedence is formulated using data-dependent grammars, which extend context-free grammars with arbitrary computation, variable binding and constraints. We implemented our approach using Iguana, a data-dependent parsing framework, and evaluated it by parsing Java and OCaml source files. The results show that our approach is practical for parsing programming languages with complicated operator precedence rules.