yabasic.1

Linux下VB解释器

.TH yabasic 1
.SH NAME
yabasic - yet another Basic
.SH SYNOPSIS
yabasic [options] [filename [arguments]]
.SH DESCRIPTION
Yabasic is a simple, old fashioned basic interpreter with
some additional features like subroutines and libraries.
Graphics and printing are limited but very easy to use.

Yabasic is documented within the file yabasic.htm, which
may or may not be present on your system; in any case this
document can be found on www.yabasic.de.

However, this html-document has been inserted as a preformatted text into this man page. Note, that you will at least need an eighty-column terminal to read this text without ugly wrapped lines.

Moreover, this man-page contains some chapters, that are specific for windows and do not directly apply to your system.

Finally note, that this man-page (unlike the html-document it is based upon) does not contain hyperlinks. In fact due to its large number of hyperlinks the html-document is much easier to read, understand and navigate than this man-page. However if you are determined to read this man-page, there are three especially useful ways to navigate; each works by searching for specific strings:

.IP \(bu 4
To go to a specific chapter (e.g. Chapter 5, "All commands and functions of yabasic"), you may look up the number of this chapter in the table of contents and search for the string "\fBChapter 5.\fR"; please note the uppercase "C" and the dot.

.IP \(bu 4
To go to the description of a specific command (e.g. the \fBfor\fR-command), you may search for its name followed by a single space and a double hyphen. In the example this would be "\fBfor --\fR".

.IP \(bu 4
The description of functions contain the name of the function followed by parens ("\fB()\fR"). Therefore, to find the description of the sine-function, you should search for "\fBsin\\(\\) --\fR". Note, that you will probably need to escape those parens by prepending them with a backslash ("\fB\\\fR").

.in 1v

But now for the documentation itself:    

.nf


Yabasic
     _________________________________________________________________

   Table of Contents

   1. Introduction

        About this document
        About yabasic

   2. The yabasic-program under Windows

        Starting yabasic
        Options
        The context Menu

   3. The yabasic-program under Unix

        Starting yabasic
        Options
        Setting defaults

   4. Some features of yabasic, explained by topic

        print, input and others
        Control statements: loops, if and switch
        Drawing and painting
        Reading from and writing to files
        Subroutines and Libraries
        String processing
        Arithmetic
        Data and such
        Other interesting commands.

   5. All commands and functions of yabasic listed by topic

        Number processing and conversion
        Conditions and control structures
        Data keeping and processing
        String processing
        File operations and printing
        Subroutines and libraries
        Other commands
        Graphics and printing

   6. All commands and functions of yabasic grouped alphabetically

        A
        B
        C
        D
        E
        F
        G
        H
        I
        L
        M
        N
        O
        P
        R
        S
        T
        U
        V
        W
        X
        Special characters
        Reserved Words

   7. A grab-bag of some general concepts and terms

        Logical shortcuts
        Conditions and expressions
        References on arrays
        Specifying Filenames under Windows
        Escape-sequences
        Creating a standalone program from your yabasic-program

   8. A few example programs

        A very simple program
        The demo of yabasic

   9. The Copyright of yabasic

Chapter 1. Introduction

   About this document
   About yabasic

About this document

   This document describes yabasic. You will find information about the yabasic
   interpreter (the program yabasic under Unix or yabasic.exe under Windows) as
   well as the language (which is, of course, a sort of basic) itself.

   This document applies to version 2.760 of yabasic

   However, this document does not contain the latest news about yabasic or a
   FAQ. As such information tends to change rapidly, it is presented online
   only at www.yabasic.de.

   Although basic has its reputation as a language for beginning programmers,
   this is not an introduction to programming at large. Rather this text
   assumes, that the reader has some (moderate) experience with writing and
   starting computer programs.

About yabasic

   yabasic is a traditional basic interpreter. It understands most of the
   typical basic-constructs, like goto, gosub, line numbers, read, data or
   string-variables with a trailing '$'. But on the other hand, yabasic
   implements some more advanced programming-constructs like subroutines or
   libraries (but not objects). yabasic works much the same under Unix and
   Windows.

   yabasic puts emphasis on giving results quickly and easily; therefore simple
   commands are provided to open a graphic window, print the graphics or
   control the console screen and get keyboard or mouse information. The
   example below opens a window, draws a circle and prints the graphic:
open window 100,100
open printer
circle 50,50,40
text 10,50,"Press any key to get a printout"
clear screen
inkey$
close printer
close window

   This example has fewer lines, than it would have in many other programming
   languages. In the end however yabasic lacks behind more advanced and modern
   programming languages like C++ or Java. But as far as it goes it tends to
   give you results more quickly and easily.

Chapter 2. The yabasic-program under Windows

   Starting yabasic
   Options
   The context Menu

Starting yabasic

   Once, yabasic has been set up correctly, there are three ways to start it:
    1. Rightclick on your desktop: The desktop menu appears with a submenu
       named new. From this submenu choose yabasic. This will create a new icon
       on your desktop. If you rightclick on this icon, its context menu will
       appear; choose Execute to execute the program.
    2. As a variant of the way described above, you may simply create a file
       with the ending .yab (e.g. with your favorite editor). Everything else
       then works as described above.
    3. From the start-menu: Choose yabasic from your start-menu. A
       console-window will open and you will be asked to type in your program.
       Once you are finished, you need to type return twice, and yabasic will
       parse and execute your program.

Note
       This is not the preferred way of starting yabasic ! Simply because the
       program, that you have typed, can not be saved and will be lost
       inevitably ! There is no such thing as a save-command and therefore no
       way to conserve the program, that you have typed. This mode is only
       intended for quick hacks, and short programs.

Options

   Under Windows yabasic will mostly be invoked by double-clicking on an
   appropriate icon; this way you do not have a chance to specify any of the
   commandline options below. However, advanced users may add some of those
   options to the appropriate entries in the registry.

   All the options below may be abbreviated, as long as the abbreviation does
   not become ambiguous. For example, you may write -e instead of -execute.

   -help or -?
          Prints a short help message, which itself describes two further
          help-options.

   -version
          Prints the version of yabasic.

   -geometry +X-POSITION+Y-POSITION
          Sets the position of the graphic window, that is opened by open
          window (the size of this window, of course, is specified within the
          open window-command). An example would be -geometry +20+10, which
          would place the graphic window 10 pixels below the upper border and
          20 pixels right of the left border of the screen. This value cannot
          be changed, once yabasic has been started.

   -font NAME-OF-FONT
          Name of the font, which will be used for graphic-text; can be any of
          decorative, dontcare, modern, roman, script, swiss. You may append a
          fontsize (measured in pixels) to any of those fontnames; for example
          -font swiss30 chooses a swiss-type font with a size of 30 pixels.

   -bind NAME-OF-STANDALONE-PROGRAM
          Create a standalone program (whose name is specified by
          NAME-OF-STANDALONE-PROGRAM) from the yabasic-program, that is
          specified on the commandline. See the section about creating a
          standalone-program for details.

   -execute A-PROGRAM-AS-A-SINGLE-STRING
          With this option you may specify some yabasic-code to be executed
          rigth away.This is useful for very short programs, which you do not
          want to save within a file. If this option is given, yabasic will not
          read any code from a file. Let's say, you have forgotten some of the
          square numbers between 1 and 10; in this case the command yabasic -e
          'for a=1 to 10:print a*a:next a' will give you the answer
          immediately.

   -infolevel INFOLEVEL
          Change the infolevel of yabasic, where INFOLEVEL can be one of debug,
          note, warning, error and fatal (the default is warning). This option
          changes the amount of debugging-information yabasic produces.
          However, normally only the author of yabasic (me !) would want to
          change this.

   -doc NAME-OF-A-PROGRAM
          Print the embedded documentation of the named program. The embedded
          documentation of a program consists of all the comments within the
          program, which start with the special keyword doc. This documentation
          can also be seen by choosing the corresponding entry from the
          context-menu of any yabasic-program.

   -librarypath DIRECTORY-WITH-LIBRARIES
          Change the directory, wherein libraries will be searched and imported
          (with the import-command). See also this entry for more information
          about the way, libraries are searched.

The context Menu

   Like every other icon under Windows, the icon of every yabasic-program has a
   context menu offering the most frequent operations, that may be applied to a
   yabasic-program.

   Execute
          This will invoke yabasic to execute your program. The same happens,
          if you doubleclick on the icon.

   Edit
          notepad will be invoked, allowing you to edit your program.

   View docu
          This will present the embedded documentation of your program.
          Embedded documentation is created with the special comment doc.

Chapter 3. The yabasic-program under Unix

   Starting yabasic
   Options
   Setting defaults

Starting yabasic

   If your system administrator (vulgo root) has installed yabasic correctly,
   there are three ways to start it:
    1. You may use your favorite editor (emacs, vi ?) to put your program into
       a file (e.g. foo). Make sure that the very first line starts with the
       characters '#!' followed by the full pathname of yabasic (e.g.
       '#!/usr/local/bin/yabasic'). This she-bang-line ensures, that your Unix
       will invoke yabasic to execute your program (see also the entry for the
       hash-character). Moreover, you will need to change the permissions of
       your yabasic-program foo, e.g. chmod u+x foo. After that you may invoke
       yabasic to invoke your program by simply typing foo (without even
       mentioning yabasic). However, if your PATH-variable does not contain a
       single dot ('.') you will have to type the full pathname of your
       program: e.g. /home/ihm/foo (or at least ./foo).
    2. Save your program into a file (e.g. foo) and type yabasic foo. This
       assumes, that the directory, where yabasic resides, is contained within
       your PATH-variable.
    3. Finally your may simply type yabasic (maybe it will be necessary to
       include its full pathname). This will make yabasic come up and you will
       be asked to type in your program. Once you are finished, you need to
       type return twice, and yabasic will parse and execute your program.

Note
       This is not the preferred way of starting yabasic ! Simply because the
       program, that you have typed, can not be saved and will be lost
       inevitably ! There is no such thing as a save-command and therefore no
       way to conserve the program, that you have typed. This mode is only
       intended for quick hacks, and short programs, i.e. for using yabasic as
       some sort of fancy desktop calculator.

Options

   yabasic accepts a number of options on the commandline. All these options
   below may be abbreviated, as long as the abbreviation does not become
   ambigous. For example you may write -e instead of -execute.

   -help or -?
          Prints a short help message, which itself describes two further
          help-options.

   -version
          Prints the version of yabasic.

   -fg FOREGROUND-COLOR or -foreground FOREGROUND-COLOR
          Define the foreground color for the graphics-window (that will be
          opened with open window). The usual X11 colornames, like red, green,
          ... are accepted. This value cannot be changed, once yabasic has been
          started.

   -bg BACKGROUND-COLOR or -background BACKGROUND-COLOR
          Define the background color for the graphics-window. The usual X11
          colornames are accepted. This value cannot be changed, once yabasic
          has been started.

   -geometry +X-POSITION+Y-POSITION
          Sets the position of the graphic window, that is opened by open
          window (the size of this window, of course, is specified with the
          open window-command). An example would be +20+10, which would place
          the graphic window 10 pixels below the upper border and 20 pixels
          right of the left border of the screen. Note, that the size of the
          window may not be specified here (well it may, but it will be ignored
          anyway). This value cannot be changed, once yabasic has been started.

   -display BACKGROUND-COLOR
          Specify the display, where the graphics window of yabasic should
          appear. Normally, however this value will be already present within
          the environment variable DISPLAY.

   -font NAME-OF-FONT
          Name of the font, which will be used for text within the graphics
          window.

   -execute A-PROGRAM-AS-A-SINGLE-STRING
          With this option you may specify some yabasic-code to be executed
          rigth away.This is useful for very short programs, which you do not
          want to save to a file. If this option is given, yabasic will not
          read any code from a file. E.g.

yabasic -e 'for a=1 to 10:print a*a:next a'

          prints the square numbers from 1 to 10.

   -bind NAME-OF-STANDALONE-PROGRAM
          Create a standalone program (whose name is specified by
          NAME-OF-STANDALONE-PROGRAM) from the yabasic-program, that is
          specified on the commandline. See the section about creating a
          standalone-program for details.

   -infolevel INFOLEVEL
          Change the infolevel of yabasic where INFOLEVEL can be one of debug,
          note, warning, error and fatal (the default is warning). This option
          changes the amount of debugging-information yabasic produces.
          However, normally only the author of yabasic (me !) would want to
          change this.

   -doc NAME-OF-A-PROGRAM
          Print the embedded documentation of the named program. The embedded
          documentation of a program consists of all the comments within the
          program, which start with the special keyword doc.

   -librarypath DIRECTORY-WITH-LIBRARIES
          Change the directory from which libraries will be imported (with the
          import-command). See also this entry for more information about the
          way, libraries will be searched.

Setting defaults

   If you want to set some options once for all, you may put them into your
   X-Windows resource file. This is usually the file .Xresources or some such
   within your home directory (type man X for details).

   Here is a sample section, which may appear within this file:
yabasic*foreground: blue
yabasic*background: gold
yabasic*geometry: +10+10
yabasic*font: 9x15

   This will set the foreground color of the graphic-window to blue and the
   background color to gold. The window will appear at position 10,10 and the
   text font will be 9x15.

Chapter 4. Some features of yabasic, explained by topic

   print, input and others
   Control statements: loops, if and switch
   Drawing and painting
   Reading from and writing to files
   Subroutines and Libraries
   String processing
   Arithmetic
   Data and such
   Other interesting commands.

   This chapter has sections for some of the major features of yabasic and
   names a few commands related with each area. So, depending on your interest,
   you find the most important commands of this area named; the other commands
   from this area may then be discovered through the links in the see
   also-section.

print, input and others

   The print-command is used to put text on the text screen. Here, the term
   text screen stands for your terminal (under Unix) or the console window
   (under Windows).

   At the bottom line, print simply outputs its argument to the text window.
   However, once you have called clear screen you may use advanced features
   like printing colors or copying areas of text with getscreen$ or putscreen.

   You may ask the user for input with the input-command; use inkey$ to get
   each key as soon as it is pressed.

Control statements: loops, if and switch

   Of course, yabasic has the goto- and gosub-statements; you may go to a label
   or a line number (which is just a special kind of label). goto, despite its
   bad reputation ([goto considered harmful]), has still its good uses; however
   in many cases you are probably better off with loops like repeat-until,
   while-wend or do-loop; you may leave any of these loops with the
   break-statement or start the next iteration immediately with continue.

   Decisions can be made with the if-statement, which comes either in a short
   and a long form. The short form has no then-keyword and extends up to the
   end of the line. The long form extends up to the final endif and may use
   some of the keywords then (which introduces the long form), else or elsif.

   If you want to test the result of an expression against many different
   values, you should probably use the switch-statement.

Drawing and painting

   You need to call open window before you may draw anything with either line,
   circle, rectangle or triangle; all of these statements may be decorated with
   clear or fill. If you want to change the colour for drawing, use colour.
   Note however, that there can only be a single window open at any given
   moment in time.

   Everything you have drawn can be send to your printer too, if you use the
   open printer command.

   To allow for some (very) limited version of animated graphics, yabasic
   offers the commands getbit$ and putbit, which retrieve rectangular regions
   from the graphics-window into a string or vice versa.

   If you want to sense mouse-clicks, you may use the inkey$-function.

Reading from and writing to files

   Before you may read or write a file, you need to open it; once you are done,
   you should close it. Each open file is designated by a simple number, which
   might be stored within a variable and must be supplied if you want to access