Communications of the ACM
Communications of the ACM
GEDANKEN—a simple typeless language based on the principle of completeness and the reference concept
Communications of the ACM
Correspondence between ALGOL 60 and Church's Lambda-notation: part I
Communications of the ACM
The next 700 programming languages
Communications of the ACM
Report on the programming language Euclid
ACM SIGPLAN Notices
ACM Transactions on Programming Languages and Systems (TOPLAS)
SIGPLAN '86 Proceedings of the 1986 SIGPLAN symposium on Compiler construction
Abstract types have existential type
ACM Transactions on Programming Languages and Systems (TOPLAS)
Abstract types have existential types
POPL '85 Proceedings of the 12th ACM SIGACT-SIGPLAN symposium on Principles of programming languages
Making variables abstract: an equational theory for Russell
POPL '83 Proceedings of the 10th ACM SIGACT-SIGPLAN symposium on Principles of programming languages
On the unification of data and program abstraction in Ada
POPL '83 Proceedings of the 10th ACM SIGACT-SIGPLAN symposium on Principles of programming languages
Data types, parameters and type checking
POPL '80 Proceedings of the 7th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
SLIPE '85 Proceedings of the ACM SIGPLAN 85 symposium on Language issues in programming environments
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In his recent Turing Lecture, John Backus delivered a trenchant argument for the proposition that "programming languages are in trouble." Backus claims this to be inevitable: the development of Algol-like languages must lead to this sorry state because it begins from faulty assumptions.A less radical interpretation of the difficulties of language design is that we still do not understand the fundamental principles that should guide our design efforts; the machines we use may limit our results, but our ignorance has far greater effect. As evidence to support this position, we can cite the difficulties of building successors to Algol 60 and Pascal. Both languages have been acclaimed as well-designed, but it has proved extremely difficult to capture just what they "got right." Thus, Hoare has claimed that "Algol 60 was not only a great improvement on its predecessors, but also on nearly all of its successors." [73a] The recent Ada design suggests that the same fate may befall Pascal.In this paper, we expand on an idea of Landin [66] to develop an important principle of programming languages: type-completeness. We argue that application of this principle is an effective tool in understanding problems of programming language design. In particular, type-completeness1. allows us to point out many of the flaws and inconsistencies in existing languages (so we can know what mistakes not to repeat) and2. provides a framework for the design of languages (or language families) that have wide variation in their changeable parts.Below, we present the principle of type-completeness and its ramifications for language design. We then discuss some common examples of incompleteness found in existing Algol-like languages. And we end by presenting the type structure of the type-complete programming language Russell, which has been designed by the authors. As we show, the flexibility provided in Russell by the combination of a small, rich type structure and type-completeness belie Backus's assertion of inherent weakness of vonNeumann languages.