Yabasic

Yabasic

File:Samegame yabasic example.png Yabasic running an implementation of SameGame.
Developer(s)	Marc-Oliver Ihm (ret.) Pedro Sá Thomas Larsen
Stable release	2.763 / August, 2007
Operating system	Windows, Unix
Type	Programming
License	GNU General Public License version 3 or later
Website	www.yabasic.de - original version to V 2.763 yabasic.basicprogramming.org - version 3

Yabasic (Yet Another BASIC) is a free and open source BASIC interpreter for Windows and Unix platforms. Yabasic was originally developed by Marc-Oliver Ihm, who released the last stable version 2.763 in 2005. Version 3 is developed by a team centered around Pedro Sá and Thomas Larsen. The Yabasic interpreter is quite compact at about 250 kilobytes total.

History

Yabasic started as a very simple interpreter around May 1995. When it was released as version 1.0 it lacked many features like arrays and loops. In summer 1996, Yabasic was ported to the Win32 platform (Version 2.0). Further improvements were the addition of subroutines and libraries (summer 1999, version 2.57), and graphic capabilities.

In August 2007, Ihm stated that "probably (he) will not develop Yabasic any further (beyond version 2.763) within the foreseeable future", due to a lack of time. Sá and Larsen have revived the project, and currently work on Yabasic 3, and on releasing bugfixes for version 2.763. Several beta releases of version 3 have been released since December 2009.

Features

• No line numbers,
• Line graphics in colour,
• Structured programming—various block structures, named subroutines with local variables and return values,
• Code modules/libraries with separate namespaces (On the other hand, composite data structures are missing),
• Option to use a graphical user interface based on the GTK library,
• Self-modifying code (see section below)
• "Binding" a Yabasic program to the interpreter, creating a standalone executable in a single file.

Passing of arguments is always by value, except for arrays, which are always passed by reference.

The interpreter is very lenient in syntactical matters—for example, both color and colour are legal variants for the same command. Likewise, there are a number of different versions for if and for constructs, giving the programmer freedom of choice in their design.

Yabasic 3

The most significant change from version 2 to version 3 is the introduction of user-defined data types.

Yabasic's idiosyncratic way of accessing system variables with peek and poke-commands has been dropped in favour of reserved variable names. Old-style BASIC control flow features (goto, gosub, labels) are no longer supported. Declaration of variables prior to use can optionally be enforced.

Examples

The classic Hello World program looks like this in Yabasic,

print "Hello World"

The following example will calculate prime numbers,

print "This program will calculate the prime numbers below the limit"
input "limit: " limit
n=2
do
  for i=2 to sqrt(n)
    if (frac(n/i)=0) then
      notprime=1
      break
    endif
  next i
  if notprime<>1 then
    print n
  endif
  notprime=0
  n=n+1
  if n>limit break
loop

Self-modifying code

String variables can be "compiled" into program code at runtime, allowing for self-modifying code.

For example, the sequence

x$= "sub printme() \n print \"Hello world!\" \n end sub"
compile(x$)

would create a new procedure,

sub printme()
 print "Hello world!"
end sub

while the program is running. This procedure can from this point on be invoked in either the 'traditional' way,

printme()

or via the slightly more clever:

y$= "printme()"
execute(y$)

Other versions

Flyab

A port of Yabasic to the Fltk toolkit called "Flyab" is currently under development. While "Flyab" only runs on BeOS at present, ports for Windows, Mac OS X, and Linux are planned. Flyab adds the ability to Yabasic to create native graphical user interfaces on all supported platforms. (As of November 2008, the project appears to be halted.)

PlayStation 2

Sony also packaged a version of Yabasic for the PlayStation 2 with all PS2 consoles in PAL territories.

External links

• Official Yabasic website — downloads and documentation for Yabasic 2.763.
• Yabasic 3 website - downloads and documentation for the Version 3 interpreter.
• Yabasic manual — documentation for the interpreter.
• YAB interpreter — BeOS version of Yabasic.
• Yabsic PS2 — site about the PS2 version.
• Small collection of Yabasic programs.