Algol Genes

In 1969 a “Report on the Algorithmic Language ALGOL 68” was published in the journal Numerische Mathematik. The authors of the report were also its designers, all academic computer scientists, Adriaan van Wijngaarden and C. H. A. Koster from the Netherlands and Barry Mailloux and John Peck from Canada. The Algol 68 project was, by then, 4 years old. The International Federation for Information Processing (IFIP) had under its umbrella a number of technical committees devoted to various specialties; each technical committee in turn had, under its jurisdiction, several working groups given to subspecialties. One such committee was the technical committee TC2, on programming; and in 1965 one of its constituent working groups WG2.1 (programming languages) mandated the development of a new international language as a successor to Algol 60. The latter, developed by an international committee of computer scientists between 1958 and 1963, had had considerable theoretical and practical impact in the first age of computer science. The Dutch mathematician-turned-computer scientist Adriaan van Wijngaarden, one of the codesigners of Algol 60 was entrusted with heading this task. The goal for Algol 68 was that it was to be a successor of Algol 60 and that it would have to be accepted and approved by IFIP as the “official” international programming language. Prior to its publication in 1969, the language went through a thorough process of review, first within the ranks of WG2.1, then by its umbrella body TC2, and finally by the IFIP General Assembly before being officially recommended for publication. The words review and recommendation mask the fact that the Algol 68 project manifested some of the features of the legislative process with its attendant politics. Thus, at a meeting of WG2.1 in Munich in December 1968— described by one of the Algol 68 codesigners John Peck as “dramatic”— where the Algol 68 report was to be approved by the working group, the designers presented their language proposal much as a lawmaker presents a bill to a legislative body; and just as the latter debates over the bill, oftentimes acrimoniously, before putting the bill to a vote, so also the Algol 68 proposal was debated over by members of WG2.1 and was finally voted on.

Equivalent Transformations and Regularization in Context-Free Grammars

Regularization of translational context-free grammar via equivalent transformations is a mandatory step in developing a reliable processor of a formal language defined by this grammar. In the 1970-ies, the multi-component oriented graphs with basic equivalent transformations were proposed to represent a formal grammar of ALGOL-68 in a compiler for IBM/360 compatibles. This paper describes a method of grammar regularization with the help of an algorithm of eliminating the left/right-hand side recursion of nonterminals which ultimately converts a context-free grammar into a regular one. The algorithm is based on special equivalent transformations of the grammar syntactic graph: elimination of recursions and insertion of iterations. When implemented in the system SynGT, it has demonstrated over 25% reduction of the memory size required to store the respective intermediate control tables, compared to the algorithm used in Flex/Bison parsers.