Language change and code breaks

[Guido van Rossum]

Tim Churches <tchur at optushome.com.au> writes:

> version 2.1 /* emulate Stata 2.1 */
> ...assorted old Stata code....
> version 6.5 /* emulate Stata 6.5 */
> ...newer code...
> version 7.0 /* revert to current version behaviour */
> ...code to take advantage of latest changes to syntax...

I have no doubt that we *could* implement this.  It would be fine to
only accept one version statement per module, as long as modules using
different versions could be used together.  The __future__ statement
does this.

But it's butt-ugly, and encourages keeping unmaintained code around.
It also becomes a burden on the programmer, who has to maintain all
this cruft and has to keep old manuals around etc.

I find it a last resort.  The nice thing about __future__ statements
is that eventually you will be able to take them out, unlike version
statements.

--Guido van Rossum (home page: http://www.python.org/~guido/)