Daniel Ventura

Bio: Daniel Ventura is an academic researcher from Universidade Federal de Goiás. The author has contributed to research in topics: Explicit substitution & De Bruijn sequence. The author has an hindex of 6, co-authored 22 publications receiving 125 citations. Previous affiliations of Daniel Ventura include University of Brasília.

Non-idempotent intersection types for the Lambda-Calculus

Abstract: This article explores the use of non-idempotent intersection types in the framework of the λ-calculus. Different topics are presented in a uniform framework: head normalization, weak normalization, weak head normalization, strong normalization, inhabitation, exact bounds and principal typings. The reducibility technique, traditionally used when working with idempotent types, is replaced in this framework by trivial combinatorial arguments.

Quantitative Types for the Linear Substitution Calculus

Abstract: We define two non-idempotent intersection type systems for the linear substitution calculus, a calculus with partial substitutions acting at a distance that is a computational interpretation of linear logic proof-nets. The calculus naturally express linear-head reduction, a notion of evaluation of proof nets that is strongly related to abstract machines. We show that our first (resp. second) quantitave type system characterizes linear-head, head and weak (resp. strong) normalizing sets of terms. All such characterizations are given by means of combinatorial arguments, i.e. there is a measure based on type derivations which decreases with respect to each reduction relation considered in the paper.

A Resource Aware Computational Interpretation for Herbelin's Syntax

Abstract: We investigate a new computational interpretation for an intuitionistic focused sequent calculus which is compatible with a resource aware semantics. For that, we associate to Herbelin's syntax a type system based on non-idempotent intersection types, together with a set of reduction rules ---inspired from the substitution at a distance paradigm--- that preserves and decreases the size of typing derivations. The non-idempotent approach allows us to use very simple combinatorial arguments, only based on this measure decreasingness, to characterize strongly normalizing terms by means of typability. For the sake of completeness, we also study typability and the corresponding strong normalization characterization in the reduction calculus obtained from the former one by projecting the explicit substitutions.

Strong Normalization through Intersection Types and Memory

Abstract: We characterize β-strongly normalizing λ-terms by means of a non-idempotent intersection type system. More precisely, we first define a memory calculus K together with a non-idempotent intersection type system K, and we show that a K-term t is typable in K if and only if t is K-strongly normalizing. We then show that β-strong normalization is equivalent to K-strong normalization. We conclude since λ-terms are strictly included in K-terms.

A Quantitative Understanding of Pattern Matching.

Abstract: This paper shows that the recent approach to quantitative typing systems for programming languages can be extended to pattern matching features. Indeed, we define two resource aware type systems, named U and E, for a lambda-calculus equipped with pairs for both patterns and terms. Our typing systems borrow some basic ideas from [BKRDR15], which characterises (head) normalisation in a qualitative way, in the sense that typability and normalisation coincide. But in contrast to [BKRDR15], our (static) systems also provides quantitative information about the dynamics of the calculus. Indeed, system U provides upper bounds for the length of normalisation sequences plus the size of their corresponding normal forms, while system E, which can be seen as a refinement of system U, produces exact bounds for each of them. This is achieved by means of a non-idempotent intersection type system equipped with different technical tools. First of all, we use product types to type pairs, instead of the disjoint unions in [BKRDR15], thus avoiding an overlap between "being a pair" and "being duplicable", resulting in an essential tool to reason about quantitativity. Secondly, typing sequents in system E are decorated with tuples of integers, which provide quantitative information about normalisation sequences, notably time (c.f. length) and space (c.f. size). Another key tool of system E is that the type system distinguishes between consuming (contributing to time) and persistent (contributing to space) constructors. Moreover, the time resource information is remarkably refined, because it discriminates between different kinds of reduction steps performed during evaluation, so that beta reduction, substitution and matching steps are counted separately.

Non-idempotent intersection types for the Lambda-Calculus

Abstract: This article explores the use of non-idempotent intersection types in the framework of the λ-calculus. Different topics are presented in a uniform framework: head normalization, weak normalization, weak head normalization, strong normalization, inhabitation, exact bounds and principal typings. The reducibility technique, traditionally used when working with idempotent types, is replaced in this framework by trivial combinatorial arguments.

Reasoning About Call-by-need by Means of Types

Abstract: We first develop a (semantical) characterization of call-by-need normalization by means of typability, i.e. we show that a term is normalizing in call-by-need if and only if it is typable in a suitable system with non-idempotent intersection types. This first result is used to derive a new completeness proof of call-by-need w.r.t. call-by-name. Concretely, we show that call-by-need and call-by-name are observationally equivalent, so that in particular, the former turns out to be a correct implementation of the latter.