24 research outputs found

    Foundations of Software Science and Computation Structures

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    This open access book constitutes the proceedings of the 25th International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2022, which was held during April 4-6, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 23 regular papers presented in this volume were carefully reviewed and selected from 77 submissions. They deal with research on theories and methods to support the analysis, integration, synthesis, transformation, and verification of programs and software systems

    Continuous Functions on Final Comodels of Free Algebraic Theories

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    In 2009, Ghani, Hancock and Pattinson gave a tree-like representation of stream processors A[N] → B[N]. In 2021, Garner showed that this representation can be established in terms of algebraic theory and comodels: the set of infinite streams A[N] is the final comodel of the algebraic theory of A-valued input [T][A] and the set of stream processors Top(A[N] , B[N]) can be seen as the final [T][A]-[T][B]-bimodel. In this paper, we generalize Garner's results to the case of free algebraic theories

    Stream processors and comodels

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    In 2009, Hancock, Pattinson and Ghani gave a coalgebraic characterisation of stream processors ANBNA^\mathbb{N} \to B^\mathbb{N} drawing on ideas of Brouwerian constructivism. Their stream processors have an intensional character; in this paper, we give a corresponding coalgebraic characterisation of extensional stream processors, i.e., the set of continuous functions ANBNA^\mathbb{N} \to B^\mathbb{N}. Our account sites both our result and that of op. cit. within the apparatus of comodels for algebraic effects originating with Power-Shkaravska. Within this apparatus, the distinction between intensional and extensional equivalence for stream processors arises in the same way as the the distinction between bisimulation and trace equivalence for labelled transition systems and probabilistic generative systems.Comment: 24 pages; v4: final accepted versio

    Continuous Functions on Final Comodels of Free Algebraic Theories

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    In 2009, Ghani, Hancock and Pattinson gave a tree-like representation of stream processors ANBNA^{\mathbb{N}} \rightarrow B^{\mathbb{N}}. In 2021, Garner showed that this representation can be established in terms of algebraic theory and comodels: the set of infinite streams ANA^{\mathbb{N}} is the final comodel of the algebraic theory of AA-valued input TA\mathbb{T}_A and the set of stream processors Top(AN,BN)\mathit{Top}(A^{\mathbb{N}},B^{\mathbb{N}}) can be seen as the final TA\mathbb{T}_A-TB\mathbb{T}_B-bimodel. In this paper, we generalize Garner's results to the case of free algebraic theories.Comment: 17 page

    Programming Languages and Systems

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    This open access book constitutes the proceedings of the 29th European Symposium on Programming, ESOP 2020, which was planned to take place in Dublin, Ireland, in April 2020, as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The actual ETAPS 2020 meeting was postponed due to the Corona pandemic. The papers deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

    Stream Processors and Comodels

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    In 2009, Ghani, Hancock and Pattinson gave a coalgebraic characterisation of stream processors A^? ? B^? drawing on ideas of Brouwerian constructivism. Their stream processors have an intensional character; in this paper, we give a corresponding coalgebraic characterisation of extensional stream processors, i.e., the set of continuous functions A^? ? B^?. Our account sites both our result and that of op. cit. within the apparatus of comodels for algebraic effects originating with Power-Shkaravska

    Towards a Uniform Theory of Effectful State Machines

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    Using recent developments in coalgebraic and monad-based semantics, we present a uniform study of various notions of machines, e.g. finite state machines, multi-stack machines, Turing machines, valence automata, and weighted automata. They are instances of Jacobs' notion of a T-automaton, where T is a monad. We show that the generic language semantics for T-automata correctly instantiates the usual language semantics for a number of known classes of machines/languages, including regular, context-free, recursively-enumerable and various subclasses of context free languages (e.g. deterministic and real-time ones). Moreover, our approach provides new generic techniques for studying the expressivity power of various machine-based models.Comment: final version accepted by TOC

    Runners in action

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    Runners of algebraic effects, also known as comodels, provide a mathematical model of resource management. We show that they also give rise to a programming concept that models top-level external resources, as well as allows programmers to modularly define their own intermediate "virtual machines". We capture the core ideas of programming with runners in an equational calculus λcoop\lambda_{\mathsf{coop}}, which we equip with a sound and coherent denotational semantics that guarantees the linear use of resources and execution of finalisation code. We accompany λcoop\lambda_{\mathsf{coop}} with examples of runners in action, provide a prototype language implementation in OCaml, as well as a Haskell library based on λcoop\lambda_{\mathsf{coop}}.Comment: ESOP 2020 final version + online appendi
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