Fundamental Concepts in Programming Languages. Christopher Strachey (1967). - PowerPoint PPT Presentation
TOWARDS A PHILOSOPHY OF COMPUTER SCIENCE
Fundamental Concepts in Programming Languages. Christopher
Strachey (1967) I am not only temperamentally a Platonist and prone
to talking about abstracts if I think they throw light on a
discussion, but I also regard syntactical problems as essentially
irrelevant to programming languages at their present state of
development. In a rough and ready sort of way, it seems to be fair
to think of the semantics as being what we want to say and the
syntax as how to say it. In these terms the urgent task in
programming languages is to explore the field of semantic
possibilities. When we have discovered the main outlines and the
principal peaks we can go about describing a suitable neat and
satisfactory notation for them. But first we must try to get a
better understanding of the processes of computing and their
description in programming languages. In computing we have what I
believe to be a new field of mathematics which is at least as
important as that opened up by the discovery (or should it be
invention) of calculus.
Lectures given at the International Summer School in Computer
Programming at Copenhagen in August, 1967. Published in
Higher-Order and Symbolic ComputationVolume 13 , Issue 1-2 (April
2000)1 SEMANTICS AND ONTOLOGYFOR PROGRAMMING
LANGUAGESOutlineGrammar and its LimitationsNormative
SemanticsMetacircular InterpretersMachinesInformal
SemanticsOperational SemanticsTowards a Theory of
OperationsProgramming Languages as Theories of Computation
3GRAMMAR and its LIMITATIONS4Grammar Syntax is given via a
formal grammar of some sort e.g., context free, BNF, inference
rules, Syntax diagrams, graphical means.But a grammar only pins
down what the legal strings of the language are. It does not
determine what they mean.We shall illustrate some issues with the
following toy programming language.
5Presumably some of the information necessary to use the
language to construct correct programs. Indeed, it must go some way
to determining what the latter is5The While Language P::= x:=E |
skip | P; P | if B then P else P | while B do P | E::= x | 0 | 1 |
E+E | EE | B::= x | true | false | E
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