Modular Language Processors
			   As Framework Completions


			       Guruduth Banavar
				Gary Lindstrom

				 UUCS-93-026

			Department of Computer Science
			      University of Utah
			 Salt Lake City, UT 84112 USA

			       October 21, 1993


				   Abstract

The conceptual and specificational power of denotational semantics for
programming language design has been amply demonstrated.  We report here on a
language implementation method that is similarly semantically motivated, but
is based upon object-oriented design principles, and results in flexible and
evolvable language processors.  We apply this technique to the area of
object-oriented (O-O) languages, in the form of a general metalevel
architecture for objects and inheritance that facilitates the development of
compilers and interpreters for O-O languages.  This development strategy
maintains architectural modularity by mapping conceptual language design
decisions to isolatable parts of resulting language processors.  Our
architecture, which is presented as an O-O framework, is characterized by (i)
support for a broad set of modularity features including encapsulation and
strong typing, and (ii) an ``unbundled'' view of inheritance, semantic
features of which are decomposed by means of a set of module combination
operations (combinators).  We describe an implementation of our framework in
C++, and assess its utility by constructing a compiler for a simple O-O
extension to the programming language C.  We further argue the flexibility of
the resulting processor by outlining the incorporation of several significant
extensions to the basic module language.  We claim that the use of such a
framework for compiler construction has many advantages, including a
systematic language development method, processor software reuse, language
extensibility, and potential for interoperability among languages.

				    NOTE

This paper is now obsolete, having been superceded by Technical Report
UUCS-94-035.