Steelman and the verifiability of (preliminary) ADA
ACM SIGPLAN Notices
Rationale for the design of the Ada programming language
ACM SIGPLAN Notices - Rationale for the deisgn of the Ada programming language
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Tartan is an experiment in language design. The goal was to determine whether a "simple" language could meet substantially all of the Ironman requirement for a common high-order programming language.We undertook this experiment because we believed that all the designs done in the first phase of the DOD effort were too large and too complex. We saw that complexity as a serious failure of the designs: excess complexity in a programming language can interiere with its use, even to the extent that any beneficial properties are of little consequence. We wanted to find out whether the requirements inherently lead to such complexity or whether a substantially simpler language would suffice.Three ground rules drove the experiment. First, no more than two months -- April 1 to May 31 -- would be devoted to the project. Second, the language would meet all the Ironman requirements except for a few points at which it would anticipate Steelman requirements. Further, the language would contain no extra features unless they resulted in a simpler language. Third, simplicity would be the overriding objective.The resulting language, Tartan, is based on all available information, including the designs already produced. The language definition is presented here; a companion report provides an overview of the language, a number of examples, and more expository explanations of some of the language features.We believe that Tartan is a substantial improvement over the earlier designs, particularly in its simplicity. There is, of course, no objective measure of simplicity, but the syntax, the size of the definition, and the number of concepts required are all smaller in Tartan.Moreover, Tartan substantially meets all of the Ironman requirement. (The exceptions lie in a few places where we anticipated Steelman requirements and where details are still missing from this report.) Thus, we believe that a simple language can meet the Ironman requirement. Tartan is an existence proof of that.We must emphasize again that this effort is an experiment, not an attempt to compete with DOD contractors. Tartan is, however, an open challenge to the Phase II contractors: The language can be at least this simple! Can you do better?