Coercion as a Metaphor for Computatiion

The idea of coercion { taking objects of one type and transforming them into objects of another { is not a new one, and has been an important feature of language design since the advent of Fortran. This paper considers a generalization of coercion that permits structured transformations between program and data structures. The nature of these coercions goes signiicantly beyond what is found in most modern programming languages. Our intention is to develop a programming model that permits the expression of a wide-range of superrcially-diverse modularity constructs within a simple and uniied framework. We base the design of this model on the observation that a variety of program structures found in modern programming languages are represented fundamentally in terms of an environment. Given suitable transformations that map the environment representation of a program structure into a data object, we can enable the programmer to gain explicit control over his naming environment. We investigate the semantics of program/data coercion in the presence of a non-strict parallel evaluation semantics for environments. Parallelism and program/data coercion form an interesting symbiosis and it is the investigation of their interaction that forms the primary focus of this paper.