Polymorphisme (informatique)

Résumé

En informatique et en théorie des types, le polymorphisme, du grec ancien polús (plusieurs) et morphê (forme), est le concept consistant à fournir une interface unique à des entités pouvant avoir différents types. Par exemple, des opérations telles que la multiplication peuvent ainsi être étendues à des scalaires aux vecteurs ou aux matrices, l'addition, des scalaires aux fonctions ou aux chaînes de caractères, etc. Il existe plusieurs sortes de polymorphismes fondamentalement différents : Selon le langage informatique employé, le polymorphisme peut être réalisé par différents moyens, inhérents au langage ou par emploi de patrons de conception. Polymorphisme ad hoc Le polymorphisme ad hoc ou surcharge de fonction consiste à déclarer plusieurs fonctions ou méthodes ayant le même nom, mais des paramètres différents (par leur nombre ou leurs types). Selon que le langage est typé statiquement ou dynamiquement, la détermination de la bonne implémentation pour les paramètres d

Source officielle

https://fr.wikipedia.org/wiki/Polymorphisme_(informatique)

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Miniboxing: An Encoding for Specialization

Cristian Talau

In the presence of parametric polymorphism, erasure-based languages such as Java and Scala handle primitives (boolean values, integers and floating point numbers) in a suboptimal way: in order to provide a uniform representation on the low level, all primitive values are stored in heap objects, in a process known as boxing. This leads to access overheads, wasteful usage of the heap space and broken cache locality. Specialization enables Scala to optimally handle primitive values in the context of generic classes, but this is done at the expense of duplicating classes up to 10 times for each type parameter, for each of the 9 Scala primitive types and heap objects. This prevents specialization of key classes in the Scala library, such as Function2, List, Map and so on. This project aims at testing the hypothesis that encoding several primitive types into a larger stack-based primitive type can maintain the performance of specialized code, while dramatically decreasing the generated bytecode size.

2012

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Lightweight Polymorphic Effects

Philipp Haller, Martin Odersky, Lukas Rytz

Type-and-effect systems are a well-studied approach for reasoning about the computational behavior of programs. Nevertheless, there is only one example of an effect system that has been adopted in a wide-spread industrial language: Java’s checked exceptions. We believe that the main obstacle to using effect systems in day-to-day programming is their verbosity, especially when writing functions that are polymorphic in the effect of their argument. To overcome this issue, we propose a new syntactically lightweight technique for writing effect-polymorphic functions. We show its independence from a specific kind of side-effect by embedding it into a generic and extensible framework for checking effects of multiple domains. Finally, we verified the expressiveness and practicality of the system by implementing it for the Scala programming language.

Springer-Verlag2012

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Working with Ada 9X classes

Ada 9X refines the Ada 83 concept of class and introduces class-wide types to support run-time polymorphism. We study how the Ada definition of class compares to other definitions of this term. We examine how run-time polymorphism is introduced in Ada 9X, how it relates to the different concepts of subtype, and how it compares with other forms of polymorphism. We also discuss the different uses of class-wide types, mainly as a means for dynamic binding (dispatching). However, since Ada 9X has adhered to the philosophy of building blocks, class-wide entities can be used for other purposes than dispatching. These uses are idioms that every programmer should be aware of. Some of these idioms are presented here. We also examine how classes are integrated with generics.

ACM Press1994

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