SNOBOL

SNOBOL4 (StriNg Oriented symBOlic Language number 4) is the fourth and final incarnation of a series of special purpose programming languages for character string manipulation. These languages were developed between 1962 and 1967 at AT&T Bell Laboratories by David J. Farber[?], Ralph E. Griswold[?] and Ivan P. Polonsky[?].

The SNOBOL4 language supports a number of built-in data types, such as integers and limited precision real numbers, strings, patterns, arrays, and tables[?], and also allows the programmer to define additional data types and new functions. It stands apart from the mainstream programming languages of that time 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.

A SNOBOL4 pattern can be very simple or extremely complex. A simple pattern is just a text string (e.g. "ABCD"), but a complex pattern may be a large structure describing, for example, the complete grammar of a computer language.

SNOBOL provides the programmer with a rich assortment of features including some rather exotic ones. As a result it is possible to use SNOBOL as if it were an object-oriented language, a logical programming language, a functional language or a standard imperative language by changing the set of features used to write a program.

It is normally implemented as an interpreter because of the difficulty in implementing some of its very high-level features, but there is a compiler, SPITBOL, which provides nearly all the facilities that the interpreter provides.

In the 1970s and 1980s, SNOBOL4 was widely used as a text manipulation language in the humanities. In recent years, its popularity has faded as newer and more efficient languages such as Awk and Perl have made string manipulation by means of regular expressions popular. SNOBOL 4 is now a special interest language used mainly by enthusiasts. The Icon programming language is a descendant of SNOBOL4.

Further Reading

• Griswold, Ralph E., J. F. Poage, and I. P. Polensky. The SNOBOL 4 Programming Language. Englewood Cliffs, NJ: Prentice Hall, 1968.
• Hockey, Susan M. Snobol Programming for the Humanities. New York: Clarendon Press; Oxford: Oxford University Press, 1985.

External Links

• http://www.snobol4.com/ -- Catspaw, Inc. offers implementations of and support for SNOBOL4
• http://www.snobol4.org/ -- Phil Budne's page of resources

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