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Polymorphic symmetric multiple dispatch with variance

Authors:

Guy L. Steele Jr.,

Sukyoung RyuAuthors Info & Claims

Proceedings of the ACM on Programming Languages, Volume 3, Issue POPL

Article No.: 11, Pages 1 - 28

https://doi.org/10.1145/3290324

Published: 02 January 2019 Publication History

Abstract

Many object-oriented languages provide method overloading, which allows multiple method declarations with the same name. For a given method invocation, in order to choose what method declaration to invoke, multiple dispatch considers the run-time types of the arguments. While multiple dispatch can support binary methods (such as mathematical operators) intuitively and consistently, it is difficult to guarantee that calls will be neither ambiguous nor undefined at run time, especially in the presence of expressive language features such as multiple inheritance and parametric polymorphism. Previous efforts have formalized languages that include such features by using overloading rules that guarantee a unique and type-sound resolution of each overloaded method call; in many cases, such rules resolve ambiguity by treating the arguments asymmetrically. Here we present the first formal specification of a strongly typed object-oriented language with symmetric multiple dispatch, multiple inheritance, and parametric polymorphism with variance. We define both a static (type- checking) semantics and a dynamic (dispatching) semantics and prove the type soundness of the language, thus demonstrating that our novel dynamic dispatch algorithm is consistent with the static semantics. Details of our dynamic dispatch algorithm address certain technical challenges that arise from structural asymmetries inherent in object-oriented languages (e.g., classes typically declare ancestors explicitly but not descendants).

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Cited By

Kudasov NSim V(2022)Formalizing ϕ-Calculus: A Purely Object-Oriented Calculus of Decorated ObjectsProceedings of the 24th ACM International Workshop on Formal Techniques for Java-like Programs10.1145/3611096.3611103(29-36)Online publication date: 7-Jun-2022
https://dl.acm.org/doi/10.1145/3611096.3611103
HUANG XZHAO JOLIVEIRA B(2021)Taming the Merge OperatorJournal of Functional Programming10.1017/S095679682100018631Online publication date: 2-Nov-2021
https://doi.org/10.1017/S0956796821000186
Belyakova JMurray TErnst G(2019)Decidable tag-based semantic subtyping for nominal types, tuples, and unionsProceedings of the 21st Workshop on Formal Techniques for Java-like Programs10.1145/3340672.3341115(1-11)Online publication date: 15-Jul-2019
https://dl.acm.org/doi/10.1145/3340672.3341115

Index Terms

Polymorphic symmetric multiple dispatch with variance
1. Social and professional topics
  1. Professional topics
    1. History of computing
      1. History of programming languages
2. Software and its engineering
  1. Software notations and tools
    1. General programming languages

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cover image Proceedings of the ACM on Programming Languages

Proceedings of the ACM on Programming Languages Volume 3, Issue POPL

January 2019

2275 pages

EISSN:2475-1421

DOI:10.1145/3302515

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Copyright © 2019 Owner/Author.

This work is licensed under a Creative Commons Attribution-NoDerivs International 4.0 License.

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Association for Computing Machinery

New York, NY, United States

Publication History

Published: 02 January 2019

Published in PACMPL Volume 3, Issue POPL

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Cited By

Kudasov NSim V(2022)Formalizing ϕ-Calculus: A Purely Object-Oriented Calculus of Decorated ObjectsProceedings of the 24th ACM International Workshop on Formal Techniques for Java-like Programs10.1145/3611096.3611103(29-36)Online publication date: 7-Jun-2022
https://dl.acm.org/doi/10.1145/3611096.3611103
HUANG XZHAO JOLIVEIRA B(2021)Taming the Merge OperatorJournal of Functional Programming10.1017/S095679682100018631Online publication date: 2-Nov-2021
https://doi.org/10.1017/S0956796821000186
Belyakova JMurray TErnst G(2019)Decidable tag-based semantic subtyping for nominal types, tuples, and unionsProceedings of the 21st Workshop on Formal Techniques for Java-like Programs10.1145/3340672.3341115(1-11)Online publication date: 15-Jul-2019
https://dl.acm.org/doi/10.1145/3340672.3341115

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