C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/vol_200/251_01/advsys.doc

Text File | 1987-10-27 | 31KB | 1,189 lines

                      ADVSYS - An Adventure Writing System

                                  Version 1.2

                                 by David Betz
                              114 Davenport Avenue
                              Manchester, NH 03103
                             [phone] (home)

                                 July 14, 1986

                       Copyright (c) 1986, by David Betz
                              All Rights Reserved
        Permission is hereby granted for unrestricted non-commercial use

















































        ADVSYS            An Adventure Writing System             Page 2


        INTRODUCTION

        ADVSYS is a special purpose programming language that was
        specifically designed to be used to write computer text
        adventure games.  It includes a facility for defining the kinds
        of objects that are common in adventures.  Some objects
        represent locations on the game map, some objects represent
        things that the player can find while exploring the adventure
        world, and some objects represent other characters that the
        adventurer can encounter during his or her journeys.  The
        adventure language also provides a facility to define actions.
        Actions are short sections of code that determine what happens
        in response to a command from the player.  These two concepts,
        "objects" and "actions" form the basis for the adventure
        language.


        ACKNOWLEDGEMENTS

        Although I have written all of the code associated with this
        adventure writing system, I must acknowledge the assistance of
        one individual without whom this project would probably never
        have reached completion.  That person is Gary McGath.  Gary was
        interested in writing a commercial quality adventure game and I
        convinced him to write it using my system (which was as yet
        almost completely unspecified) instead of using a traditional
        programming language.  The input that Gary provided during the
        development of his game contributed significantly to the overall
        design of the system.  I would like to thank Gary for that
        contribution.

































        ADVSYS            An Adventure Writing System             Page 3


        USING THE SYSTEM TO WRITE AN ADVENTURE

        In order to write an adventure using this system, you need to
        write an adventure description.  This is an ordinary ASCII text
        file containing definitions for all of the objects and actions
        in your adventure game.  This file is used as input to the
        adventure compiler.  The compiler takes the adventure
        description and compiles it into a set of data structures.

        In order to play an adventure written using this system, you
        need the data structure file that was produced by the compiler
        and the adventure interpreter program.  The interpreter uses the
        information produced by the adventure compiler to allow a player
        to play the adventure game.  Notice that it is not necessary for
        the player to have access to the original adventure description
        file.  All of the information that is necessary to play the
        adventure game is contained within the data structure file that
        is produced by the compiler.  This file is a binary file that
        cannot be simply "listed" to reveal the internal workings of the
        adventure.

        The adventure compiler is called ADVCOM and the interpreter is
        called ADVINT.  These two programs in conjunction with this
        documentation are all that is required to write and play
        adventure games using this system.






































        ADVSYS            An Adventure Writing System             Page 4


        RUNNING THE COMPILER

        If you have created an adventure definition file called
        "MYADV.ADV", you can compile it with the command:

                A>advcom myadv

        Typing this command will invoke the adventure compiler and cause
        it to compile the file named "MYADV.ADV".  The ".ADV" extension
        is added to the file name by the compiler.  During the process
        of compiling the file, many messages will be printed telling
        about the progress of the compiler.  At the end of the
        compilation process, the compiler prints a set of statistics
        describing the resulting data structure file.  This file will be
        called "MYADV.DAT".  It contains the data structures needed by
        the adventure interpreter to allow a player to play the
        adventure game.

        Note: The "A>" in the line above is the MS-DOS prompt and should
        not be typed as part of the command.


        RUNNING THE INTERPRETER

        Assuming that you have a compiled adventure data file called
        "MYADV.DAT", you can play the adventure by typing the command:

                A>advint myadv

        This command will start the adventure.  There will probably be
        some text printed at this point describing the adventure and the
        initial situation.  You will then be prompted to type a command.
        The prompt is the colon character.  The format for commands is
        described under the section about the parser.  After typing a
        command, you will be told what happened as a result of your
        command, your new situation will be described and you will begin
        the loop again.


























        ADVSYS            An Adventure Writing System             Page 5


        ADVENTURE DESCRIPTION FILE FORMAT

            All adventure description files contain a collection of
            statements.  These statements must be formed according to
            the following rules:


        The adventure definition statement:

            All adventure definitions should have an ADVENTURE
            statement.  This statement gives the name of the adventure
            and the version number of the definition file.  Each
            adventure should have a unique name.  This name is used to
            identify "saved position" files and insure that only files
            that correspond to the current adventure are restored.  The
            version number allows the author to have many versions of
            the same adventure during development and guarantee that
            "save" files from one version aren't restored into another
            version.

              (ADVENTURE name version)

          Example:

              (ADVENTURE sample 1)


        Vocabulary statements:

            These statements add words to the adventure vocabulary.

              (ADJECTIVE word*)
              (PREPOSITION word*)
              (CONJUNCTION word*)
              (ARTICLE word*)
              (SYNONYM word synonym*)

          Examples:

              (ADJECTIVE red blue)
              (CONJUNCTION and)
              (SYNONYM big large)

          Note:

              Words are also added to the vocabulary by the object
              and action definitions using the NOUN, ADJECTIVE, VERB
              and PREPOSITION statements.















        ADVSYS            An Adventure Writing System             Page 6


        Constant definition statement:

              (DEFINE name value)

          Examples:

              (DEFINE what "I don't understand what you're saying!\n")
              (DEFINE max-load 100)


        Function definition statement:

              (DEFINE (function-name [arg-name]* [&aux tmp-name*]) expr*)

          Example:

              (DEFINE (factorial n)
                (IF (< n 2)
                  1