Abstraction mechanisms in CLU

TLDR

CLU is a new language that supports procedural, control, and data abstractions, a need highlighted by programming methodology research that finds only procedural abstraction is well supported by conventional languages. The paper introduces CLU’s abstraction mechanisms. CLU offers novel linguistic mechanisms for data and control abstractions and a type‑checked library that enables incremental program development. Programming examples demonstrate how CLU’s mechanisms enable the use and implementation of procedural, control, and data abstractions in program construction.

Abstract

CLU is a new programming language designed to support the use of abstractions in program construction. Work in programming methodology has led to the realization that three kinds of abstractions—procedural, control, and especially data abstractions—are useful in the programming process. Of these, only the procedural abstraction is supported well by conventional languages, through the procedure or subroutine. CLU provides, in addition to procedures, novel linguistic mechanisms that support the use of data and control abstractions. This paper provides an introduction to the abstraction mechanisms in CLU. By means of programming examples, the utility of the three kinds of abstractions in program construction is illustrated, and it is shown how CLU programs may be written to use and implement abstractions. The CLU library, which permits incremental program development with complete type checking performed at compile time, is also discussed.