Rodrigo Ribeiro

Federal University of Ouro Preto · Departament of Computer Science (DECOM)

Haskell is a statically-typed, purely functional programming language with a strong academic foundation, widely recognized for its application in both research and industry for developing robust, high-assurance software. Nowadays, it is being adopted for a variety of projects, where applications reach a level of complexity where manual testing and...

Programming languages are popular and diverse, and the convenience of programmatically changing the behavior of complex systems is attractive even for the ones with stringent security requirements, which often impose restrictions on the acceptable programs. A very common restriction is that the program must terminate, which is very hard to check be...

Simulations applied in the educational context are capable of providing considerable support in the learning process of a given area of knowledge. This work proposes the development of an interactive, free and open source simulation software for educational use in the context of Linear Systems Modeling and Analysis. Within the scope of the discipli...

We describe the formalization of Brzozowski and Antimirov derivative based algorithms for regular expression parsing, in the dependently typed language Agda. The formalization produces a proof that either an input string matches a given regular expression or that no matching exists. A tool for regular expression based search in the style of the wel...

Featherweight Java is one of the most popular calculi which specify object-oriented programming features. It has been used as the basis for investigating novel language functionalities, as well as to specify and understand the formal properties of existing features for languages in this paradigm. However, when considering mechanized formalization,...

Formal models are important tools in the programming language research community. However, such models are full of intricacies and, due to that, they are subject to subtle errors. Such failures motivated the usage of tools to ensure the correctness of these formalisms. One way to eliminate such errors is to encode models in a dependently-typed lang...

Este resumo tem como objetivo fomentar a discussão sobre a importância do uso de ferramentas computacionais para o ensino de lógica formal em cursos de Bacharelado em Ciência da Computação. Em especial, sugerimos a utilização de assistentes de provas para o desenvolvimento das habilidades presentes em conteúdos introdutórios de lógica e matemática...

Type inference is a feature that is common to a variety of programming languages. While, in the past, it has been prominently present in functional ones (e.g., ML and Haskell), today, many object-oriented/multi-paradigm languages such as C# and C++ offer, to a certain extent, such a feature. Nevertheless, type inference still is an unexplored subje...

Formal models are important tools in the programming language research community. However, such models are full of intricacies and, due to that, they are subject to subtle errors. Such failures motivated the usage of tools to ensure the correctness of these formalisms. One way to eliminate such errors is to encode models in a dependently-typed lang...

We describe the formalization of Brzozowski and Antimirov derivative based algorithms for regular expression parsing, in the dependently typed language Agda. The formaliza-tion produces a proof that either an input string matches a given regular expression or that no matching exists. A tool for regular expression based search in the style of the we...

Consistency is a key property of any logical system. However, proofs of consistency usually rely on heavy proof theory notions like admissibility of cut. A more semantics-based approach to consistency proofs explores the correspondence between a logic and its relationship with the evaluation in a λ-calculus, known as Curry-Howard isomorphism. In th...

Unification is the core of type inference algorithms for modern functional programming languages, like Haskell and SML. As a first step towards a formalization of a type inference algorithm for such programming languages, we present a formalization in Coq of a type unification algorithm that follows classic algorithms presented in programming langu...

Property-based testing of compilers or programming language semantics is difficult to accomplish because it is hard to design a random generator for valid programs. Most compiler test tools do not have a well-specified way for generating type-correct programs, which is a requirement for such testing activities. In this project, we formalize a type-...

HMusic is a domain specific language based on music patterns that can be used to write music and live coding. The main abstractions provided by the language are patterns and tracks. Code written in HMusic looks like patterns and multi-tracks available in music sequencers, drum machines and DAWs. HMusic provides primitives to design and combine patt...

Featherweight Java is one of the most popular calculi which specify object-oriented programming features. It has been used as the basis for investigating novel language functionalities, as well as to specify and understand the formal properties of existing features for languages in this paradigm. However, when considering mechanized formalization,...

We describe the formalization of a type system for parsing expression grammars (PEG) which is equivalent to Ford's original fixpoint-based definition of well-formed PEGs. We use our type system definition to implement a functional big-step semantics for typed PEGs using the Agda programming language.

Adaptable Parsing Expression Grammars (APEG) are a formal model whose main purpose is to formally describe the syntax of extensible languages and their extension mechanisms. APEG extends Parsing Expression Grammar model with the notion of syntactic attributes, which are values passed through parse tree nodes and used during the parsing process. A g...

Currently, Java is one of the most used programming language, being adopted in many large projects, where applications reach a level of complexity for which manual testing and human inspection are not enough to guarantee quality in software development. Even when using automated unit tests, such tests rarely cover all interesting cases of code, whi...

Regular expressions (REs) are pervasive in computing. We use REs in text editors, string search tools (like GNU-Grep) and lexical analysers generators. Most of these tools rely on converting regular expressions to its corresponding finite state machine or use REs derivatives for directly parse an input string. In this work, we investigate the suita...

The release of Java 8 represents one of the most significant updates to the Java language since its inception. The addition of λ-expressions allows the treatment of code as data in a compact way, improving the language expressivity. This paper addresses the problem of defining rigorous semantics for new features of Java, such as λ-expressions and d...

Support for generalized algebraic data types (GADT) in extensions of Haskell allows functions defined over GADTs to be written without the need for type annotations in some cases, but it requires type annotations in most of them. This paper presents a type inference algorithm for GADTs that extends OutsideIn algorithm using anti-unification to capt...

The objective of this paper is twofold: first, we discuss the state of art on Java-like semantics, focusing on those that provide formal specification using operational semantics (big-step or small-step), studying in detail the most cited projects and presenting some derivative works that extend the originals aggregating useful features. Also, we f...

Incomplete source code naturally emerges in software development: during the design phase, while evolving, testing and analyzing programs. Therefore, the ability to understand partial programs is a valuable asset. However, this problem is still unsolved in the C programming language. Difficulties stem from the fact that parsing C requires, not only...

This paper describes HDrum, a Domain Spe- cific Language for writing drum patterns. Pro- grams written in HDrum look similar to the grids, available in sequencers and drum machines, used to program drum beats, but as the language has an inductive definition we can write abstrac- tions to manipulate drum patterns. HDrum is embedded in the Haskell fu...

We describe the formalization of a regular expression (RE) parsing algorithm that produces a bit representation of its parse tree in the dependently typed language Agda. The algorithm computes bit-codes using Brzozowski derivatives and we prove that produced codes are equivalent to parse trees ensuring soundness and completeness w.r.t an inductive...

We describe the formalization of a certified algorithm for regular expression parsing based on Brzozowski derivatives, in the dependently typed language Idris. The formalized algorithm produces a proof that an input string matches a given regular expression or a proof that no matching exists. A tool for regular expression based search in the style...

This paper explores an approach for allowing type classes to be optionally declared by programmers, i.e. programmers can overload symbols without declaring their types in type classes. The type of an overloaded symbol is, if not explicitly defined in a type class, automatically determined from the anti-unification of instance types defined for the...

This paper considers the problem of ambiguity in Haskell-like languages. Overloading resolution is characterized in the context of constrained polymorphism by the presence of unreachable variables in constraints on the type of the expression. A new definition of ambiguity is presented, where existence of more than one instance for the constraints o...

Nowadays the support of generalized algebraic data types (GADTs) in extensions of Haskell allows functions defined over GADTs to be written without the need for type annotations in some cases and requires type annotations in other cases. In this paper we present a type inference algorithm for GADTs that is based on a closed-world approach to overlo...

Unification is the core of type inference algorithms for modern functional programming languages, like Haskell. As a first step towards a formalization of a type inference algorithm for such programming languages, we present a formalization in Coq of a type unification algo- rithm that follows classic algorithms presented in programming language te...

Algorithms for constraint set satisfiability and simplification of Haskell type class constraints are used during type inference in order to allow the inference of more accurate types and to detect ambiguity. Unfortunately, both constraint set satisfiability and simplification are in general undecidable, and the use of these algorithms may cause no...

As computer programs become increasingly complex, techniques for ensuring trustworthiness of information manipulated by them become critical. In this work, we use the Coq proof assistant to formalise a $\lambda $ λ -calculus with trust types, originally formulated by Ørbæk and Palsberg. We give formal proofs of type soundness, erasure and simul...

This paper discusses ambiguity in the context of languages that support context-dependent overloading, such as Haskell. A type system for a Haskell-like programming language that supports context-dependent overloading and follow the Hindley-Milner approach of providing context-free type instantiation, allows distinct derivations of the same type fo...

The introduction of multi-parameter type classes in Haskell has been hindered because of problems associated to ambiguity, which occur due to the lack of type specialization during type inference. This paper proposes a mini- malist, simple solution to this problem, which requires only a small change to the type inference algorithm and to what has b...