Integrating Nominal and Structural Subtyping

Malayeri, Donna; Aldrich, Jonathan

doi:10.1007/978-3-540-70592-5_12

Cited by 36 publications

(34 citation statements)

References 17 publications

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“…Nevertheless, structural types offer their own advantages [20,21]. For instance, structural types are flexible and compositional, providing better support for unanticipated reuse.…”

Section: Nominal Typesmentioning

confidence: 99%

“…This is because they imply a more flexible subtyping relationship compared to nominal subtyping, allowing unrelated classes in the class hierarchy to be subtypes. Taking this into account, some type systems [9,22,20] use structural types. In fact, a nominal type also can be considered in terms of its structural representation.…”

Section: Nominal Typesmentioning

confidence: 99%

“…Gradualtalk supports the combination of nominal and structural types, similar to Unity [20] and Scala [23]. 3 A type combines both a nominal part and a structural part, as in A{m1...mn}.…”

Section: Reconciling Nominal and Structural Typesmentioning

confidence: 99%

See 2 more Smart Citations

Gradual typing for Smalltalk

Allende

Callaú

Fabry

et al. 2014

Science of Computer Programming

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Being able to combine static and dynamic typing within the same language has clear benefits in order to support the evolution of prototypes or scripts into mature robust programs. While being an emblematic dynamic object-oriented language, Smalltalk is lagging behind in this regard. We report on the design, implementation and application of Gradualtalk, a gradually-typed Smalltalk meant to enable incremental typing of existing programs. The main design goal of the type system is to support the features of the Smalltalk language, like metaclasses and blocks, live programming, and to accomodate the programming idioms used in practice. We studied a number of existing projects in order to determine the features to include in the type system. As a result, Gradualtalk is a practical approach to gradual types in Smalltalk, with a novel blend of type system features that accomodate most programming idioms.

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“…Nevertheless, structural types offer their own advantages [20,21]. For instance, structural types are flexible and compositional, providing better support for unanticipated reuse.…”

Section: Nominal Typesmentioning

confidence: 99%

Section: Nominal Typesmentioning

confidence: 99%

See 1 more Smart Citation

Gradual typing for Smalltalk

Allende

Callaú

Fabry

et al. 2014

Science of Computer Programming

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show abstract

“…In a language where subtyping is nominal, A is a subtype of B if and only if it is declared to be so, meaning if class A extends (or implements) class (or interface) B; these relations must be defined by the programmer and are based on the names of classes and interfaces declared. Java programmers are used to nominal subtyping, but other languages [12,14,18,19,20,22,24] are based on the structural approach. In the latter, subtyping relation is established only by analyzing the structure of a class, i.e.…”

Section: Structuralmentioning

confidence: 99%

“…its fields and methods: a class A is a subtype of a class B if and only if the fields and methods of A are a superset of the fields and methods of B, and their types in A are subtypes of their types in B. Even though the syntactic subtyping is more naturally linked to the nominal one, the former can also be adapted to support the structural one, as shown in [14,19]. In this paper we follow the reverse direction and give another contribution.…”

Section: Structuralmentioning

confidence: 99%

Semantic Subtyping for Objects and Classes

Dardha

Gorla

Varacca

2013

Formal Techniques for Distributed Systems

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Abstract.We propose an integration of structural subtyping with boolean connectives and semantic subtyping to define a Java-like programming language that exploits the benefits of both techniques. Semantic subtyping is an approach to defining subtyping relation based on set-theoretic models, rather than syntactic rules. On the one hand, this approach involves some non trivial mathematical machinery in the background. On the other hand, final users of the language need not know this machinery and the resulting subtyping relation is very powerful and intuitive. While semantic subtyping is naturally linked to the structural one, we show how the framework can also accommodate the nominal subtyping. Several examples show the expressivity and the practical advantages of our proposal.

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SFJ: An Implementation of Semantic Featherweight Java

Usov

Dardha

2020

Lecture Notes in Computer Science

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There are two approaches to defining subtyping relations: the syntactic and the semantic approach. In semantic subtyping, one defines a model of the language and an interpretation of types as subsets of this model. Subtyping is defined as inclusion of subsets denoting types. An orthogonal subtyping question, typical of object-oriented languages, is the nominal versus the structural subtyping. Dardha et al. [11, 12] defined boolean types and semantic subtyping for Featherweight Java (FJ) and integrated both nominal and structural subtyping, thus exploiting the benefits of both approaches. However, these benefits were illustrated only at a theoretical level, but not exploited practically. We present SFJ-Semantic Featherweight Java, an implementation of FJ which features boolean types, semantic subtyping and integrates nominal as well as structural subtyping. The benefits of SFJ, illustrated in the paper and the accompanying video (with audio/subtitles) [27], show how static type-checking of boolean types and semantic subtyping gives higher guarantees of program correctness, more flexibility and compactness of program writing.

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Integrating Nominal and Structural Subtyping

Cited by 36 publications

References 17 publications

Gradual typing for Smalltalk

Gradual typing for Smalltalk

Semantic Subtyping for Objects and Classes

SFJ: An Implementation of Semantic Featherweight Java

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