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Communications of the ACM

Communications of the ACM

Syntactic and semantic augments to ALGOL

The purpose of this paper is to propose a set of syntactic and semantic augments to ALGOL. The proposed extension are designed to facilitate the description of “string” manipulation in that language; they do not constitute a comprehensive language for symbol manipulation. Several such languages (LISP, IPL, …) already exist—many more will be designed and advantageously used in the future. It is felt that such languages belong in the repertoire of some language-system which contains a hierarchy of languages as well as nested “continua” of languages. In such systems, new languages may be embedded, appended, extracted at will. The fact that ALGOL is, implicitly, such a language-system seems to be only dimly recognized, even by designers. In any event, what is proposed in the sequel is not a language for symbol manipulation—qua language; but rather, a set of obvious extensions to the “algebraic-language” portion of ALGOL. To be sure, these extensions are complete in the sense that they are sufficient to describe symbol manipulations, but after all, the same statement holds for machine-language. Moreover, the extensions do not constitute a minimal set of primitives for string or symbol manipulations—in the sense that complementation, shifting, … are primitives for machine arithmetic. Such primitives are essential only to machine designers (including designers of “augmented machine”, the basic machine augmented by subroutines for arithmetics not included in the hardware); to append only such primitives to ALGOL is to visit the omissive sins of the machine designers upon the users of ALGOL.

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