Generative Binary Components

Most software component technologies fail to account for lightweight components (those for which a function call is too ineecient or semantically inappropriate) or generative components (those in which the component embodies a method of constructing code rather than actual code). Macro-based systems such as the C++ Standard Template Library are exceptions. They, however, have the disadvantage that components must be delivered largely in source form. In this paper, we present a framework for component technologies, in which lightweight and generative components can be delivered in binary form. The technology is conceptually simple and is easily implemented with existing programming languages. Our basic idea is this: By giving a compositional semantics for a source language in a domain of meanings Code, components can be written in the form of macros, but communicated in terms of meanings. An implementation of the framework is obtained by providing a speciic deenition of Code. We show by several examples how higher-order values over Code can be used to write lightweight, generative components. We describe some possible deenitions of Code, and discuss in detail a prototype implementation in which Code is deened so as to generate eecient code for Sparc machines.