SNOBOL

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{math, number, function}
{system, computer, user}
{language, word, form}
{theory, work, human}

SNOBOL (String Oriented Symbolic Language) is a generic name for the computer programming languages developed between 1962 and 1967 at AT&T Bell Laboratories by David J. Farber, Ralph E. Griswold and Ivan P. Polonsky, culminating in SNOBOL4. It was one of a number of text-string-oriented languages developed during the 1950s and 1960s; others included COMIT and TRAC.

SNOBOL4 stands apart from most programming languages by having patterns as a first-class data type (i.e. a data type whose values can be manipulated in all ways permitted to any other data type in the programming language) and by providing operators for pattern concatenation and alternation. Strings generated during execution can be treated as programs and executed.

SNOBOL4 was quite widely taught in larger US universities in the late 1960s and early 1970s and was widely used in the 1970s and 1980s as a text manipulation language in the humanities.

In recent years its use has faded as newer languages such as AWK and Perl have made string manipulation by means of regular expressions fashionable. SNOBOL4 patterns subsume BNF grammars, which are equivalent to context-free grammars and more powerful than regular expressions.[1] The "regular expressions" in current versions of AWK and Perl are in fact extensions of regular expressions in the traditional sense, but regular expressions, unlike SNOBOL4 patterns, cannot be recursive, which gives a distinct computational advantage to SNOBOL4 patterns.[2]

One of the designers of SNOBOL, Ralph Griswold, designed successors to SNOBOL4 called SL5 and Icon, which combined the backtracking of SNOBOL4 pattern matching with more standard ALGOL-like structuring, as well as adding some features of their own.

Contents

Development

The initial SNOBOL language was created as a tool to be used by its authors to work with the symbolic manipulation of polynomials. It was written in assembly language for the IBM 7090. It had a simple syntax, only one datatype, the string, no functions, and no declarations and very little error control. However despite its simplicity and its "personal" nature its use began to spread to other groups. As a result the authors decided to extend it and tidy it up. They rewrote it and added functions, both standard and user-defined, and released the result as SNOBOL3. SNOBOL2 did exist but it was a short-lived intermediate development version without user-defined functions and was never released. SNOBOL3 became quite popular and was rewritten for other computers than the IBM 7090 by other programmmers. As a result several incompatible dialects arose.

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