On the role of memory in object-based and object-oriented languages

Programming languages that support the object-oriented perspective on programming may be divided into two groups. One group of languages originating from Simula follows the Algol tradition with respect to block structure, static name binding and compile-time type checking. Another group of languages originating from Smalltalk is more in the style of the Lisp tradition with a flat set of definitions (classes), dynamic name binding and run-time type checking. The purpose of this paper is to analyze the role of block structure in object-oriented languages. It will be demonstrated that block structure is useful from both a conceptual and technical viewpoint.

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Classless Object Semantics

10.26686/wgtn.17064350 ◽

2021 ◽

Author(s):

◽

Timothy Jones

Keyword(s):

Programming Languages ◽

Object Oriented ◽

Formal Theory ◽

Theoretical Models ◽

Language Design ◽

Trade Offs ◽

Practical Design ◽

Integral Role ◽

Object Oriented Languages

<p>Objects have been categorised into classes that declare and implement their behaviour ever since the paradigm of object-orientation in programming languages was first conceived. Classes have an integral role in the design and theory of object-oriented languages, and often appear alongside objects as a foundational concept of the paradigm in many theoretical models. A number of object-oriented languages have attempted to remove classes as a core component of the language design and rebuild their functionality purely in terms of objects, to varying success. Much of the formal theory of objects that eschews classes as a fundamental construct has difficulty encoding the variety of behaviours possible in programs from class-based languages. This dissertation investigates the foundational nature of the class in the object-oriented paradigm from the perspective of an ‘objects-first’, classless language. Using the design of theoretical models and practical implementations of these designs as extensions of the Grace programming language, we demonstrate how objects can be used to emulate the functionality of classes, and the necessary trade-offs of this approach. We present Graceless, our theory of objects without classes, and use this language to explore what class functionality is difficult to encode using only objects. We consider the role of classes in the types and static analysis of object-oriented languages, and present both a practical design of brand objects and a corresponding extension of our theory that simulates the discipline of nominal typing. We also modify our theory to investigate the semantics of many different kinds of implementation reuse in the form of inheritance between both objects and classes, and compare the consequences of these different approaches.</p>

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Classless Object Semantics

10.26686/wgtn.17064350.v1 ◽

2021 ◽

Author(s):

◽

Timothy Jones

Keyword(s):

Programming Languages ◽

Object Oriented ◽

Formal Theory ◽

Theoretical Models ◽

Language Design ◽

Trade Offs ◽

Practical Design ◽

Integral Role ◽

Object Oriented Languages

<p>Objects have been categorised into classes that declare and implement their behaviour ever since the paradigm of object-orientation in programming languages was first conceived. Classes have an integral role in the design and theory of object-oriented languages, and often appear alongside objects as a foundational concept of the paradigm in many theoretical models. A number of object-oriented languages have attempted to remove classes as a core component of the language design and rebuild their functionality purely in terms of objects, to varying success. Much of the formal theory of objects that eschews classes as a fundamental construct has difficulty encoding the variety of behaviours possible in programs from class-based languages. This dissertation investigates the foundational nature of the class in the object-oriented paradigm from the perspective of an ‘objects-first’, classless language. Using the design of theoretical models and practical implementations of these designs as extensions of the Grace programming language, we demonstrate how objects can be used to emulate the functionality of classes, and the necessary trade-offs of this approach. We present Graceless, our theory of objects without classes, and use this language to explore what class functionality is difficult to encode using only objects. We consider the role of classes in the types and static analysis of object-oriented languages, and present both a practical design of brand objects and a corresponding extension of our theory that simulates the discipline of nominal typing. We also modify our theory to investigate the semantics of many different kinds of implementation reuse in the form of inheritance between both objects and classes, and compare the consequences of these different approaches.</p>

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Proceedings of the 14th Workshop on Implementation, Compilation, Optimization of Object-Oriented Languages, Programs and Systems - ICOOOLPS '19

10.1145/3340670 ◽

2019 ◽

Keyword(s):

Object Oriented ◽

Object Oriented Languages

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Exceptions in object-oriented languages

Proceedings of the 1986 SIGPLAN workshop on Object-oriented programming - ◽

10.1145/323779.323749 ◽

1986 ◽

Cited By ~ 2

Author(s):

Alexander Borgida

Keyword(s):

Object Oriented ◽

Object Oriented Languages

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Sheaf semantics for concurrent interacting objects

Mathematical Structures in Computer Science ◽

10.1017/s0960129500001420 ◽

1992 ◽

Vol 2 (2) ◽

pp. 159-191 ◽

Cited By ~ 25

Author(s):

Joseph A. Goguen

Keyword(s):

Computer Security ◽

Object Oriented ◽

Continuous Linear ◽

Sheaf Theory ◽

Electrical Circuits ◽

Object Based ◽

Time Concepts ◽

Hardware Description ◽

Description Languages ◽

Object Oriented Systems

This paper uses concepts from sheaf theory to explain phenomena in concurrent systems, including object, inheritance, deadlock, and non-interference, as used in computer security. The approach is very; general, and applies not only to concurrent object oriented systems, but also to systems of differential equations, electrical circuits, hardware description languages, and much more. Time can be discrete or continuous, linear or branching, and distribution is allowed over space as well as time. Concepts from categpru theory help to achieve this generality: objects are modelled by sheaves; inheritance by sheaf morphisms; systems by diagrams; and interconnection by diagrams of diagrams. In addition, behaviour is given by limit, and the result of interconnection by colimit. The approach is illustrated with many examples, including a semantics for a simple concurrent object-based programming language.

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