[Python-Dev] Re: Stability and change (original) (raw)

Alex Martelli aleax@aleax.it
Mon, 8 Apr 2002 22:52:58 +0200

On Monday 08 April 2002 22:45, Skip Montanaro wrote:

Guido> I think version dependency management is subject to the Logajan Guido> paradox. :-(

Can you state that succintly for us? :-)

"Python keeps being maintained yet it never happens that release X (for any X and Y) can run some code that release Y cannot run".

It's unachievable (as well as unreasonable) and thus I don't think it should be considered.

A desire that I think more reasonable (still unachievable, but one can come closer) is a similar wish stated only for Y > X. In practice we do need break-points where such backwards compatibility cannot be guaranteed ("major releases") -- further, I think that for the wish to be both achievable AND compatible with other important goals it must be nuanced ('some code' becoming 'CORRECT code', for example -- broken code that HAPPENS to run by accident is quite another thing: although for some users the difference can be hard to appreciate, the concept of 'undefined behavior' is, I believe, known widely enough to rely on it a bit, at least where the docs mention it).

Alex