Type classes as objects and implicits

Oliveira, Bruno C. d. S.; Moors, Adriaan; Odersky, Martin

doi:10.1145/1932682.1869489

Cited by 41 publications

(50 citation statements)

References 42 publications

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“…This is similar to methods in objectoriented programming whose availability depends on type parameters [28], but here we see that this feature arises "mechanically" by the de/refunctionalization correspondence. We see again how both impossible equations and the need to access constructor type arguments translate naturally into corresponding features in the codata world.…”

Section: Informal Overviewsupporting

confidence: 59%

Dualizing Generalized Algebraic Data Types by Matrix Transposition

Ostermann

Jabs

2018

Programming Languages and Systems

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Abstract. We characterize the relation between generalized algebraic datatypes (GADTs) with pattern matching on their constructors one hand, and generalized algebraic co-datatypes (GAcoDTs) with copattern matching on their destructors on the other hand: GADTs can be converted mechanically to GAcoDTs by refunctionalization, GAcoDTs can be converted mechanically to GADTs by defunctionalization, and both defunctionalization and refunctionalization correspond to a transposition of the matrix in which the equations for each constructor/destructor pair of the (co-)datatype are organized. We have defined a calculus, GADT T , which unifies GADTs and GAcoDTs in such a way that GADTs and GAcoDTs are merely different ways to partition the program.We have formalized the type system and operational semantics of GADT T in the Coq proof assistant and have mechanically verified the following results: (1) The type system of GADT T is sound, (2) defunctionalization and refunctionalization can translate GADTs to GAcoDTs and back, (3) both transformations are type-and semantics-preserving and are inverses of each other, (4) (co-)datatypes can be represented by matrices in such a way the aforementioned transformations correspond to matrix transposition, (5) GADTs are extensible in an exactly dual way to GAcoDTs; we thereby clarify folklore knowledge about the "expression problem".We believe that the identification of this relationship can guide future language design of "dual features" for data and codata.

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Section: Informal Overviewsupporting

confidence: 59%

Dualizing Generalized Algebraic Data Types by Matrix Transposition

Ostermann

Jabs

2018

Programming Languages and Systems

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“…The use of Scala's mirror-based reflection requires an adjustment on the types of the combinators in Algebra. The combinators now need to take an additional implicit parameter [40] m, which contains a reflective description of type parameters. This additional parameter does not affect client code since it is implicitly inferred and passed by the Scala compiler.…”

Section: Default Combinator Implementations Using Reflectionmentioning

confidence: 99%

Feature-Oriented Programming with Object Algebras

Oliveira

Storm

Loh

et al. 2013

ECOOP 2013 – Object-Oriented Programming

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Abstract. Object algebras are a new programming technique that enables a simple solution to basic extensibility and modularity issues in programming languages. While object algebras excel at defining modular features, the composition mechanisms for object algebras (and features) are still cumbersome and limited in expressiveness. In this paper we leverage two well-studied type system features, intersection types and type-constructor polymorphism, to provide object algebras with expressive and practical composition mechanisms. Intersection types are used for defining expressive run-time composition operators (combinators) that produce objects with multiple (feature) interfaces. Type-constructor polymorphism enables generic interfaces for the various object algebra combinators. Such generic interfaces can be used as a type-safe front end for a generic implementation of the combinators based on reflection. Additionally, we also provide a modular mechanism to allow different forms of self -references in the presence of delegation-based combinators. The result is an expressive, type-safe, dynamic, delegation-based composition technique for object algebras, implemented in Scala, which effectively enables a form of Feature-Oriented Programming using object algebras.

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“…In Scala, requirements on a type parameter can be expressed with a trait. It can be implemented in a so-called object, and automatically selected for instantiation using the implicit mechanism [OMO10]. Regarding the expressive power of these approaches, all of them are comparable to our basic binding mechanism plus adapters.…”

Section: Related Workmentioning

confidence: 99%

Flexible Model-to-Model Transformation Templates: An Application to ATL.

Cuadrado¹,

Guerra²,

Lara³

2012

JOT

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Model transformation is one of the core techniques in ModelDriven Engineering. Many transformation languages exist nowadays, but few offer mechanisms directed to the reuse of whole transformations or transformation fragments in different contexts.Taking inspiration from generic programming, in this paper we define model transformation templates. These templates are not defined over concrete meta-models, but on so-called meta-model concepts which later can be bound to specific meta-models. The binding mechanism is flexible as it permits mapping concepts and meta-models with certain kinds of structural heterogeneities. The approach is general and can be applied to any model transformation language. In this paper we report on its application to ATL.

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Type classes as objects and implicits

Cited by 41 publications

References 42 publications

Dualizing Generalized Algebraic Data Types by Matrix Transposition

Dualizing Generalized Algebraic Data Types by Matrix Transposition

Feature-Oriented Programming with Object Algebras

Flexible Model-to-Model Transformation Templates: An Application to ATL.

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