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he SNOBOL4 Programming Language

The SNOBOL4 Programming Language

THE

SNOBOL

PROGRAMMING

LANGUAGE

second edition

R. E. Griswold

J. F. Poage

I. P. Polonsky

second edition

THE

SNOBOL

PROGRAMMING

LANGUAGE

R. E. Griswold

J. F. Poage

I. P. Polonsky

Bell Telephone Laboratories, Incorporated

Prentice-Hall, Inc., Englewood Cliffs, New Jersey

Reprinted electronically in 2005 by Ron Stephens & Catspaw, Inc.

by permission of AT

Permission is granted to make and distribute verbatim

copies of this book provided the copyright notice and

permission notice are preserved on all copies.

(Originally published by Prentice Hall, Inc., ISBN 13-815373-6)

Library of Congress Catalog Card Number: 70-131996

Printed in the United Stated of America

World Wide Web sites for additional SNOBOL4 material:

Catspaw, Inc.

Phil Budne’s SNOBOL4 resources

www.SNOBOL4.com

www.SNOBOL4.org

Foreword

SNOBOL4

a computer programming language containing many features not

commonly found in other programming languages.

evolved from SNOBOL [1,2,3]*, a

language for string manipulation, developed at Bell Telephone Laboratories, Incorporated,

in 1962. Extensions to SNOBOL through various versions have made it a useful tool in

such areas as compilation techniques, machine simulation, symbolic mathematics, text

preparation, natural language translation, linguistics, and music analysis.

The basic data element of SNOBOL4 is a string of characters, such as this line of

printing. The language has operations for joining and separating strings, for testing their

contents, and for making replacements in them.

a string is a sentence, it can be broken

into phrases or words.

it is a formula, it can be taken apart into components and

reassembled in another format. A string can appear either as a literal or as the value of a

variable. The literal form is indicated by enclosing the string in quotation marks:

'THIS IS A STRING'

The string value may be assigned to a variable:

LINE

'THIS IS

STRING'

A common operation on a string is examination of its contents for a desired structure of

characters. This structure, known as a pattern, can be as simple as a string or a given

number of characters. A pattern also can be an extremely complicated expression

consisting, for example, of a number of alternatives followed by another set of alternatives,

all of which must begin a given number of characters from the end of the string. The

pattern, as a data type, may also appear either in literal or variable form. The data type

of a variable - string, pattern, or any other in the language - depends on the last value

assigned to it. There are no type declaration statements for variables as in other

programming languages.

SNOBOL4 provides numerical capabilities with both integers and real numbers. Because

the language is essentially character oriented, and since most numerical operations involve

character counting, integers are more commonly used. Conversion among integers, real

numbers, and strings representing integers or real numbers is performed automatically as

required. The programmer may, in addition, define other data types, such as complex

numbers, and provide operations for them.

Often it is desirable to associate a group of items with one variable name through

numerical indexing or some other identifying property. The SNOBOL4 array and table

provide these capabilities with more flexibility than most programming languages. An

Numbers

in brackets refer to references listed at the end of this manual.

iii

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