A BASIC Interpreter - Program like it's 1979!

Basic interpreter copied from https://github.com/richpl/PyBasic and modified to run under Micropython, CircuitPython or cPython under Windows. The interpreter can be launched from PyDOS by typing "PyBasic" or from the REPL by typing "import PyBasic"

There has been a great deal of work done recently to bring most of the changes in the PyDOS version of PyBasic to the original RICHPL version. See the excellent PyBasic documentation at https://github.com/richpl/PyBasic#readme

The PyDOS version of PyBasic still has the following difference from the richpl github version:

PyDOS command line argument functionality
prompt changed from > to :
commas can be used in addition to semi-colons as print statment delimeters
starting array element 1 rather than 0, so that dim(10) created a 10 element array
PI, RNDINT, TERNARY, LEFT$, RIGHT$ functions not supported in the PyDOS version
The RND function does not take any arguments or even empty parenthesis in the PyDOS version
PyDOS version runs Basic program in place on flash rather than loading into memory
added a saved index source code option when saving or loading using the .PGM extension on a program filename, this vastly speeds up subsequent program load times
added SOUND freq,duration[,volume] command. The Windows code uses the winsound library and the Micropython/Circuit Python implementations assumes the appropriate speaker circuit is connected to the GPIO pin defined in pydos_bcfg.py