bytecode non-backcompatibility

[Terry Reedy]

"Maurice LING" <mauriceling at acm.org> wrote in message 
news:d4l825$mj7$1 at domitilla.aioe.org...
> I think backward compatibility is good enough. A Java JAR file compiled 
> under for JVM 1.2 can still run in JVM 1.4. I don't think anyone will or 
> can expect forward compatibility, that will require godly powers...

One difference between Java and Python is this: Java bytecodes are, as I 
understand it, part of the Java language definition.  CPython bytecodes are 
intentionally not part of the language at all.  Except maybe fore PyPy, 
other implementations do not use them.  Jython translates Python source to 
Java bytecodes.  Pyrex translates augmented Python source to C, to be 
compiled to native machine code.  Ironman translates, I presume, to .NET 
common language.  PyParrot (don't know if it has an official name) 
translates to Parrot bytecodes.  Viper translated to OCamel.

If you want an implementation with frozen bytecodes, you are free to make 
one ;-)

Terry J. Reedy