DeLesley Hutchins
ABSTRACT
I present the Ohmu language, a unified object model which allows a number of "advanced" techniques such as aspects, mixin layers, parametric polymorphism, and generative components to be implemented cleanly using two basic concepts: block structure and inheritance. I argue that conventional ways of defining classes and objects have created artificial distinctions which limit their expressiveness. The Ohmu model unifies functions, classes, instances, templates, and even aspects into a single construct - the structure. Function calls, instantiation, aspect-weaving, and inheritance are likewise unified into a single operation - the structure transformation. This simplification eliminates the distinction between classes and instances, and between compile-time and run-time code. Instead of being compiled, programs are reduced using partial evaluation, during which the interpreter is invoked at compile-time. Within this architecture, standard OO inheritance becomes a natural vehicle for creating meta-programs and automatic code generators - the key to a number of recent domain-driven programming methodologies.
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Index Terms
- The power of symmetry: unifying inheritance and generative programming
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Reviews
Olivier Louis Marie Lecarme
The author describes a programming language, Ohmu, as well as an object-oriented (OO) model of the same name, which unifies the concepts of functions, classes, instances, templates, and aspects into a single construct, the structure. If one considers that the first idea of OO languages was to extend and generalize the idea of a structure, this is a fortunate simplification. What I find to be the most interesting idea is that by choosing various binding times for parameters, one can specialize constructs in various ways, and obtain the same capabilities that are currently obtained using many different and restricted constructs. One of the consequences is that the programmer no longer needs to know what is done at compile time and what is done at runtime. Another one is a generalization of the type concept, which finally encompasses objects and values. In fact, if the paper had not been presented to OOPSLA, it could have avoided using the full range of OO terminology. That would make it more acceptable outside of this community. It could be interesting also to note that some of the ideas presented here could be traced back, for example, to the Euler language [1] in 1966, as well as other languages of the same period. But none of the references in this paper is older than 1987. Online Computing Reviews Service
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