Context-Free Grammars (CFGs) are a simple and intuitively appealing formalism for the description of programming languages, but lack the computational power to describe many common language features. Over the past three decades, numerous extensions of the CFG model have been developed. Most of these extensions retain a CFG kernel, and augment it with a distinct facility with greater computational power. However, in all the most powerful CFG extensions, the clarity of the CFG kernel is undermined by the opacity of the more powerful extending facility. An intuitively appealing strategy for CFG extension is grammar adaptability, the principle that declarations in a program effectively modify the context-free grammar of the programming language. An adaptable grammar is equipped with some formal means for modifying its own CFG kernel. Most previous adaptable grammar formalisms have, unfortunately, failed to realize the potential clarity of this concept. In this thesis, a representative samp...

ion in Programming --- working definition by John N. Shutt Computer Science Technical Report Series WORCESTER POLYTECHNIC INSTITUTE Computer Science Department 100 Institute Road, Worcester, Massachusetts 01609-2280 Abstraction in Programming --- working definition John N. Shutt jshutt@cs.wpi.edu Computer Science Department Worcester Polytechnic Institute Worcester, MA 01609 December 1999 Abstract This paper investigates the nature of the process in programming by which a new level of abstraction is constructed by building upon an existing one. The process is called abstraction. The purpose of the investigation is to provide an informal characterization of abstraction, as a conceptual foundation for subsequent development of a mathematical theory of abstraction. Contents 1 Introduction 1 2 Other senses of `abstraction' 1 2.1 Metaphysics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.1.1 Universals . . . . . . . . . . . . . . . . . . . . . ....