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VANILLA SNOBOL4 Vanilla SNOBOL4 provides the entire Bell Labs SNOBOL4 program- ming language, except for real numbers and external functions. The total size of the object program and data cannot exceed 30K bytes in this entry-level version. Vanilla SNOBOL4 and the ac- companying documentation are copyrighted materials. However, it may be copied and shared according to these terms: 1. No fee greater than $10 is charged for use, copying or dis- tribution. 2. SNOBOL4.EXE and all documentation are not modified in any way, and are distributed together. 3. The manual may not be packaged with any other product. 4. Neither SNOBOL4+ (our commercial product), nor its printed manual, may be copied. Vanilla SNOBOL4 was released because we believe many people would enjoy programming in SNOBOL4, if there was a version of the language that was widely and freely available. Contributions are NOT requested. Enjoy and share it! This file, VANILLA.DOC, provides an overview of the SNOBOL4 Programming Language, and why you'll find it to be an interesting and useful tool. THE PHILOSOPHY OF SNOBOL4... Like most high-level computer languages, SNOBOL4 represents a design philosophy. C, for instance, was designed for power and portability. BASIC was designed for introducing students to com- puters, and Pascal for teaching structured programming. SNOBOL4's designers felt that programming time and effort should be minimized, even if the computer had to do additional work. The philosophy is to allow the programmer to focus on solving the problem at hand, rather than on details like dynamic memory allocation, variable typing, data conversion, and so on. If ease of use coupled with extraordinary power and versatility appeals to you, please read on. VANILLA.DOC (V1.2) - 1 - Catspaw, Inc. THE STRING LANGUAGE... Almost uniquely among computer languages, SNOBOL4 treats a string as a distinct data type, rather than as a sequence or array of discrete characters. That's an abstraction. Consider a concrete example to fill an everyday need -- converting a WordStar file into an ASCII file. In most languages, your program would have to examine each character in the WordStar file. If its ASCII value is 127 or below, the character is passed on; if above, then 128 is sub- tracted. Then the individual bytes have to be reassembled into a string. Assuming that the input and output files have been designated on the command line, the entire conversion program in SNOBOL4 looks like this: &Alphabet LEN(128) . Normals LEN(128) . Highs Loop Output = REPLACE(Input, Highs, Normals) :S(Loop) Notice how the REPLACE function operates on the entire string at once? Is there any other language that could do this conver- sion in a two-line program? How much time could you save by writing data-conversion programs in SNOBOL4? THE PATTERN LANGUAGE... While SNOBOL4 provides a rich repertoire of string functions, its other specialty is patterns. Suppose, for instance, you have a list of words, and you want to write out all those that start with "b" or "d", followed by a vowel, and end in "ly". Here's the entire program: * Match at the start of a word and define a pattern: &Anchor = 1 WantPat = ('b' | 'd') ANY('aeiou') RTAB(2) 'ly' * Read a line of input, perform the match, write results: Fetch Word = Input :F(End) Word WantPat :F(Fetch) Output = Word :(Fetch) End SNOBOL4's syntax is so easy that you probably didn't need to know it to understand this program. A line can have a label, an operation, or a goto, or any two, or all three. Statements can succeed or fail. The goto can be conditional upon success or failure. In the above program, a pattern is first defined. At Fetch, the input is assigned to the variable Word. If that fails, the VANILLA.DOC (V1.2) - 2 - Catspaw, Inc. program has run out of input, and the program stops by transfer- ring to End. Next the word is compared to the pattern. If that fails, the program goes back to Fetch to get the next word. If the opera- tion succeeds, control goes to the next line, where Word is writ- ten out, and a transfer made to Fetch to continue the loop. Pattern matching is a very-high level language concept. Pat- terns may be arbitrarily complex -- SNOBOL4 will search among the many alternatives for a match. Patterns may even be recursively defined: LIST = ELEMENT | ELEMENT "," *LIST THE USEFUL LANGUAGE... The range of current uses for SNOBOL4 is as diverse as its users. Because programs can be written quickly for testing, systems-level programmers use it for prototyping assemblers, com- pilers and language translators. In many offices, the utilities for reformatting data and text are short SNOBOL4 programs. With its backtrack searching, recur- sive abilities, and first-class data objects, SNOBOL4 is finding a home in artificial-intelligence research. Its pattern-matching makes it a natural for querying data bases. Researchers use it for finding patterns in everything from medieval music to DNA sequences. Newspapers and print shops use it for text formatting, translation and typesetting. Others find SNOBOL4 the perfect tool for one-shot "throw-away" programs. If the challenge before you is primarily non-numeric, the odds are that you can use SNOBOL4 to meet that challenge more quickly and easily than with any other language. THE ELEGANT LANGUAGE... SNOBOL4 is so powerful that its programs are typically quite short. Source programs are typical 5 to 10 TIMES smaller than equivalent C or Pascal programs. SNOBOL4 allows an unlimited number of user-defined subroutines. By relying upon them, you create programs of structure and ele- gance. Like patterns, subroutines may be recursive. They're also fast to write and easy to update, revise, and maintain. THE EASY-TO-LEARN LANGUAGE... Because SNOBOL4's syntax is so simple, it's easy to learn the VANILLA.DOC (V1.2) - 3 - Catspaw, Inc. basics and be writing useful programs in just a few hours. Human- ities professors love it because its short programs are simple to explain to students without a computer background. But while it is easy to learn, it's not easy to exhaust. The concepts embodied -- patterns, success and failure, tables, recursion, run-time code compilation -- will stimulate your interest indefinitely. Whether you're a systems designer, software developer, language enthusiast, end user, or the office PC guru, you can put SNOBOL4 to work immediately to make your time more productive. THE FLEXIBLE LANGUAGE... Not only can you create your own "language within a language" with SNOBOL4's roll-your-own functions, but you can define your own data types. As if that weren't flexibility enough, SNOBOL4 also allows you to redefine or extend its operators during execution -- flexibil- ity that few other languages dare to offer. In fact, you can create and execute new program segments at runtime; programs can evolve based upon the data they are pro- cessing. It's trivial to write a SNOBOL4 program that reads, compiles and executes other SNOBOL4 programs. Try doing that in BASIC or Pascal! One of SNOBOL4's most exquisite features is the TABLE. In essence, it's a one-dimensional array where the index can be any data type. You aren't limited to A[1] or the like; your table can have indices like A["what"] or A[7.3]. The table, almost unique to SNOBOL4, provides associative mem- ory referencing -- so that data can be quickly stored and refer- enced in its natural form. THE POWERFUL AND PORTABLE LANGUAGE... Beyond its specialties of string and pattern-matching, SNOBOL4 provides a full array of mathematical operations; it's a general- purpose programming language. Pointers, indirect-referencing and user-defined data types permit arbitrary data structures such as lists, trees, and networks. Because the SNOBOL4 language has been implemented on a wide range of mainframe and mini-computer systems, programs can be developed and tested on a desktop machine, then easily ported to the bigger computers, generally with no modification. VANILLA.DOC (V1.2) - 4 - Catspaw, Inc. THE UPGRADEABLE LANGUAGE... If you become a SNOBOL4 fan, you'll want SNOBOL4+, our $125 pro- fessional version (plus shipping). It allows programs and data up to 300K, assembly-language functions, real numbers, and has dozens of extensions like: binary and random-access I/O, include files, built in Shell sort, Spitbol operators, SAVE files and royalty-free runtime, dozens of new functions and keywords and a symbolic debugger. It interfaces easily to specialized systems and components, such as Novell's Btrieve(tm) file management package. You can find more information about SNOBOL4+ in the file SNOBOL4.DOC. SNOBOL4+ includes a 240-page printed and indexed manual, and over 70 files of sample programs and functions. SNOBOL4+ is not a public-domain product, and it may not be copied (except for le- gitimate backup purposes). The printed manual may not be copied. SNOBOL4+ owners also get telephone and written support, should you ever have a question about SNOBOL4 programming. We carry all SNOBOL4 books in print, from beginner to advanced. Also available is SPITBOL, a high-performance 32-bit implementation of the SNOBOL4 language with execution speeds 6 to 10 times FASTER than SNOBOL4+. Versions are available for MS-DOS 80386/486, OS/2 2.0, Apple Macintosh, Sun 4/SPARC, and many 680x0 UNIX workstations. Enjoy this taste of SNOBOL4, the standard for text manipula- tion, pattern-matching, and fun programming. We hope you develop an appetite. CATSPAW, INC. P.O. BOX 1123 SALIDA, COLORADO 81201 USA Telephone: (719) 539-3884 FAX: (719) 539-4830 ____________________ (tm) Unix is a registered trademark of AT&T VANILLA.DOC (V1.2) - 5 - Catspaw, Inc.