Language VAX SCAN
Date: | 03/22/09 |
Author: | Gerardo Cacciari |
URL: | http://decnet.ipv7.net |
Comments: | 0 |
Info: | See source comments |
Score: | (2.91 in 11 votes) |
!++ ! ! "VAX SCAN is a block-structured programming language in the VAX/VMS ! environment that is designed to build tools to manipulate text strings and ! text files. The primary applications for VAX SCAN are filters, translators, ! extractors/analyzers, and preprocessors. VAX SCAN is a compiled programming ! language that includes string operators for searching, comparing, extracting, ! and assigning character strings. A significant strength of VAX SCAN is in the ! pattern-matching constructs that permit matching of one or more complex ! patterns of text in the input data. VAX SCAN can then create replacement text ! for the original patterns that were found in the input." ! ! The above text was taken from "Guide to VAX SCAN", order number AA-FU79C-TE ! Copyright (C) 1985, 1986, 1989 Digital Equipment Corporation. ! ! VAX SCAN is a hybrid language, being both procedural and pattern-driven. Every ! program executes in a classic imperative fashion up until a START SCAN ! statement is encountered. On such occurence, the program turns into a ! pattern-driven engine and tries to match whichever START SCAN input it ! receives to the pattern specified on trigger MACRO declarations. Matching ! macro code can then replace or even drop matched input by means of the ANSWER ! statement which in turn can optionally trigger other macros, either nested or ! not. The matching process stops whenever a STOP SCAN statement or the end of ! input stream is reached. Then the program continues in procedural mode. ! ! To better demonstrate VAX SCAN pattern-matching capabilities and syntax, this ! sample uses a START SCAN input procedure providing always the same sentence, ! plus some macros for numbering, formatting, and overall control. Nevertheless ! it could have been designed as a simple procedural program. ! ! VAX SCAN adheres to the common calling standard of the VAX/VMS operating ! system. An object created by the VAX SCAN compiler can be successfully linked ! and used in a multilanguage environment, thus allowing for projects written in ! other languages to take advantage of the particular VAX SCAN capabilities. ! ! VAX SCAN was retired as a product in 1994 and was submitted to the DECUS ! Library in 1995. It can be found in the [.VAXSCAN] directory of Freeware V4.0. ! ! Made on a VAX, 22-MAR-2009 ! !-- MODULE ninetynine_beers IDENT 'V1.0'; CONSTANT SS$_NORMAL EXTERNAL INTEGER; CONSTANT SCN$_ENDINPSTM EXTERNAL INTEGER; DECLARE thats_all: BOOLEAN; SET digit ( '0'..'9' ); TOKEN how_many { ['-'] digit... }; TOKEN bottles { [' '...] 'bottle' ['s'] }; TOKEN placeholder { '<' digit '>' }; TOKEN end_of_line { '/' }; MACRO take_one_beer TRIGGER { which,where: placeholder }; IF which = '<3>' THEN ANSWER TRIGGER STRING ( 99 - where ); ELSE ANSWER TRIGGER STRING ( 100 - where ); END IF; END MACRO; MACRO no_more_beer TRIGGER { count: how_many bottles }; CASE INTEGER ( count ) FROM 1 TO 99; [ 1 ]: ANSWER count, ' bottle'; [ INRANGE ]: ANSWER count, ' bottles'; [ OUTRANGE ]: ANSWER 'no more bottles'; thats_all = TRUE; END CASE; END MACRO; MACRO insert_carriage_returns TRIGGER { end_of_line }; ANSWER S'EOL'; END MACRO; PROCEDURE generate_song ( len: REFERENCE INTEGER, buf: REFERENCE POINTER TO FIXED STRING (132) ) OF INTEGER; DECLARE song_line: DYNAMIC STRING; song_line = '<1> bottles of beer on the wall, ' & '<2> bottles of beer./' & 'Take one down and pass it around, ' & '<3> bottles of beer on the wall./'; len = LENGTH ( song_line ); buf-> = song_line; IF thats_all THEN RETURN SCN$_ENDINPSTM; ELSE RETURN SS$_NORMAL; END IF; END PROCEDURE; PROCEDURE end_song ( ); WRITE 'No more bottles of beer on the wall, ' & 'no more bottles of beer.'; WRITE 'Go to the store and buy some more, ' & '99 bottles of beer on the wall.'; END PROCEDURE; PROCEDURE beer_song MAIN ( ); START SCAN INPUT PROCEDURE generate_song OUTPUT FILE 'SYS$OUTPUT'; CALL end_song; END PROCEDURE; END MODULE;
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