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1

Type-driven development of concurrent communicating systems

Brady E.

Computer Science

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2017

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Vol. 18 (3)

219--240

EN

Modern software systems rely on communication, for example mobile applcations communicating with a central server, distributed systems coordinaing a telecommunications network, or concurrent systems handling events and processes in a desktop application. However, reasoning about concurrent prgrams is hard, since we must reason about each process and the order in which communication might happen between processes. In this paper, I describe a type-driven approach to implementing communicating concurrent programs, using the dependently typed programming language Idris. I show how the type system can be used to describe resource access protocols (such as controlling access to a file handle) and verify that programs correctly follow those prtools. Finally, I show how to use the type system to reason about the order of communication between concurrent processes, ensuring that each end of a communication channel follows a defined protocol.

2

Modeling Contexts with Dependent Types

Dapoigny R., Barlatier P.

Fundamenta Informaticae

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2010

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Vol. 104, nr 4

293-327

EN

In the area of knowledge representation, a challenging topic is the formalization of context knowledge on the basis of logical foundations and ontological semantics. However, most attempts to provide a formal model of contexts suffer from a number of difficulties, such as limited expressiveness of representation, restricted variable quantification, lack of (meta) reasoning about properties, etc. In addition, type theory originally developed for formal modeling of mathematics has also been successfully applied to the correct specification of programs and in the semantics of natural language. In this paper, we suggest a type theoretical approach to the problem of context and action modeling. Type theory is used both for representing the system’s knowledge of the discourse domain and for reasoning about it. For that purpose, we extend an existing dependent type theory having nice properties, with context-based rules and appropriate inductive types. We claim that the resulting theory exploiting the power of dependent types is able to provide a very expressive system together with a unified theory allowing higher-order reasoning.

3

Automation for Dependently Typed Functional Programming

Wilson S., Fleuriot J., Smaill A.

Fundamenta Informaticae

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2010

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Vol. 102, nr 2

209-228

EN

Writing dependently typed functional programs that capture non-trivial program properties is difficult in current systems due to lack of proof automation. We identify proof patterns that occur when programming with dependent types and detail how automating such patterns allow us to work more comfortably with types that capture, for example, membership, ordering and nonlinear arithmetic properties. We describe the role of the rippling heuristic, both for inductive and non-inductive proofs, and generalisation in providing such automation. We then discuss an implementation of our ideas in Coq with practical examples of dependently typed programs, that capture useful program properties, which can be verified automatically. We demonstrate that our proof automation is generic in that it can provide support for working with theorems involving user-defined functions and inductive data types.

4

A Tutorial Implementation of a Dependently Typed Lambda Calculus

Löh A., McBride C., Swierstra W.

Fundamenta Informaticae

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2010

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Vol. 102, nr 2

177-207

EN

We present the type rules for a dependently typed core calculus together with a straightforward implementation in Haskell. We explicitly highlight the changes necessary to shift from a simply-typed lambda calculus to the dependently typed lambda calculus. We also describe how to extend our core language with data types and write several small example programs. The article is accompanied by an executable interpreter and example code that allows immediate experimentation with the system we describe.

5

A Note on Forcing and Type Theory

Coquand T., Jaber G.

Fundamenta Informaticae

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2010

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Vol. 100, nr 1/4

43-52

EN

The goal of this note is to show the uniform continuity of definable functional in intuitionistic type theory as an application of forcing with dependent type theory.

6

Implementing Typeful Program Transformations

Chen Ch., Shi R., Xi H.

Fundamenta Informaticae

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2006

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Vol. 69, nr 1,2

103-103

EN

The notion of program transformation is ubiquitous in programming language studies on interpreters, compilers, partial evaluators, etc. In order to implement a program transformation, we need to choose a representation in the meta language, that is, the programming language in which we construct programs, for representing object programs, that is, the programs in the object language on which the program transformation is to be performed. In practice, most representations chosen for typed object programs are typeless in the sense that the type of an object program cannot be reflected in the type of its representation. This is unsatisfactory as such typeless representations make it impossible to capture in the type system of the meta language various invariants in a program transformation that are related to the types of object programs. In this paper, we propose an approach to implementing program transformations that makes use of a first-order typeful program representation, where the type of an object program as well as the types of the free variables in the object program can be reflected in the type of the representation of the object program. We introduce some programming techniques needed to handle this typeful program representation, and then present an implementation of a CPS transform function where the relation between the type of an object program and that of its CPS transform is captured in the type system of DML. In a broader context, we claim to have taken a solid step along the line of research on constructing certifying compilers.