Java Wildcards Meet Definition-Site Variance

Altidor, John; Reichenbach, Christoph; Smaragdakis, Yannis

doi:10.1007/978-3-642-31057-7_23

Cited by 9 publications

(20 citation statements)

References 19 publications

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“…Scala uses the syntax T <: U to specify that T has an upper bound of U or that T must be subtype of U. Accordingly, T >: L is used to specify that T has a lower bound of L. Despite it is possible to write a compiler that automatically derives which type of access is used in a certain expression [AHS11], most languages offer particular variance annotations to let programmers choose if a type constructor is used invariantly, covariantly or contravariantly. Altogether, there are two main approaches to support variance annotations:…”

Section: Parametric Typesmentioning

confidence: 99%

Scaps: type-directed API search for Scala

Wegmann¹,

Mehta

Sommerlad

et al. 2016

Proceedings of the 2016 7th ACM SIGPLAN Symposium on Scala

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Reusing existing functionality from legacy code and third party programming libraries is often hard, because the vast number of definitions and the complexity of the APIs require a detailed knowledge of the programming environment. To help developers discovering such functionality when working with a statically typed, object-oriented programming language, we designed an API retrieval system that supports querying indexed APIs with textual keywords and type signatures. The feature of the search engine is inspired by a similar tool for the Haskell programming language called Hoogle. Though, we decided to develop another approach to address the API search problem based on traditional information retrieval techniques which, we argue, is better suited for object-oriented languages.As a proof of concept, we implemented the API retrieval system for the Scala programming language and provided a web-based user interface. Furthermore, we demonstrate how Scala-specific language features like user-defined implicit conversions and implicit parameters can be included into our basic approach. A comparison to a system using only exact matches of partial types of the query shows that the effectiveness of API retrieval can be substantially improved with our approach. Management SummaryThis thesis describes the design of a type directed search engine for statically-typed, object-oriented programming languages. Furthermore, we provide an implementation for the Scala programming language that incorporates Scala specific language constructs. Status QuoA crucial part of creating high quality software projects is the reuse of existing functionality provided by in-house or third party programming libraries. This ensures that functionality is not unnecessarily reimplemented and lowers the risk of introducing erroneous behavior. Code reused over various projects tends to be well-tested and battle-proofed.Discovering existing functionality is a task that requires either a deep knowledge of the according libraries or appropriate tools that provide access convenient to the definitions in a library. Some examples of such tools are code completion assistants that list the accessible members of an object in question and automatically generated documentation pages for the available classes. Though, these tools tend to give an incomplete picture of the available operations, because functionality provided through utility classes or by additional libraries are usually not listed.In this case, developers often resort to universal search engines like Google to find a specific implementation. While these search engines often provide suitable results, users have to manually mine the result pages for suitable content. Additionally, the result pages may refer to outdated revisions of a library.In the functional programming community, a popular tools to overcome these issues are search engines, like Hoogle for Haskell, that accept type signatures as search queries and retrieve definitions of a similar type. In combination with a powerful type syst...

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Section: Parametric Typesmentioning

confidence: 99%

Scaps: type-directed API search for Scala

Wegmann¹,

Mehta

Sommerlad

et al. 2016

Proceedings of the 2016 7th ACM SIGPLAN Symposium on Scala

View full text Add to dashboard Cite

show abstract

“…The entailment relation for X must respect the interpretation of (a) C(f = t) as a finite tree with root labeled with C, ith branch labeled with f i and leading to t i , and (b) t.f as selection of the child labeled f for the tree t. 2 Equality is reflexive, symmetric, transitive, and a congru-…”

Section: Constraint Systemmentioning

confidence: 99%

“…Scala [38] and C [12], by contrast, support definition-site variance annotations, which address many of the usability concerns of wildcards [26], but can often result in complicated or duplicated code to create invariant, covariant, and contravariant versions of a library class. Altidor et al [2] propose a framework for combining definitionand use-site variance in a Java-like language. Encoding this framework in FXG is an interesting area for future work.…”

Section: Related Workmentioning

confidence: 99%

Constrained kinds

et al. 2012

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Modern object-oriented languages such as X10 require a rich framework for types capable of expressing both value-dependency and genericity, and supporting pluggable, domain-specific extensions.In earlier work, we presented a framework for constrained types in object-oriented languages, parametrized by an underlying constraint system. Types are viewed as formulas C{c} where C is the name of a class or an interface and c is a constraint on the immutable instance state (the properties) of C. Constraint systems are a very expressive framework for partial information. Many (value-)dependent type systems for object-oriented languages can be viewed as constrained types.This paper extends the constrained types approach to handle type-dependency ("genericity"). The key idea is to introduce constrained kinds: in the same way that constraints on values can be used to define constrained types, constraints on types can define constrained kinds.We develop a core programming language with constrained kinds. Generic types are supported by introducing type variables-literally, variables with "type" Type-and permitting programs to impose subtyping and equality constraints on such variables. We formalize the type-checking rules and establish soundness.While the language now intertwines constraints on types and values, its type system remains parametric in the choice of the value constraint system (language and solver). We demonstrate that constrained kinds are expressive and practical and sketch possible extensions with a discussion of the design and implementation of X10.

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“…FOO is inspired by Featherweight Java (FJ) [10]: it is also a class-based formalism and emphasizes inheritance. Indeed, the motivation for FOO stems from our own past language modeling efforts [2,[7][8][9] which were based on FJ. We found that the language features that are most pertinent to our language extensions had little to do with key elements of Featherweight Java, such as casts, fields, or constructors.…”

Section: Introductionmentioning

confidence: 99%

Fᴏᴏ

Gerakios

Fourtounis

Smaragdakis

2015

Proceedings of the 17th Workshop on Formal Techniques for Java-Like Programs

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We present the Flyweight Object-Oriented (FOO) calculus for the modeling of object-oriented languages. FOO is a simple, minimal class-based calculus, modeling only essential computational aspects and emphasizing larger-scale features (e.g., inheritance and generics). FOO is motivated by the observation that recent language design work focuses on elements not well-captured either by traditional object calculi or by language-specific modeling efforts, such as Featherweight Java. FOO integrates seamlessly both nominal and structural subtyping ideas, leveraging the latter to eliminate the need for modeling object fields and constructors. Comparing to recent formalization efforts in the literature, FOO is more compact, yet versatile enough to be usable in multiple settings modeling Java, C#, or Scala extensions.

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Java Wildcards Meet Definition-Site Variance

Cited by 9 publications

References 19 publications

Scaps: type-directed API search for Scala

Scaps: type-directed API search for Scala

Constrained kinds

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