On Thu, Sep 18, 2008 at 4:56 PM, Joseph Wright
<[log in to unmask]> wrote:

>> Something like
>>   \IfOldPackageDate{2006/06/08}{...implement old functionality...}
>> )
>
> An interesting idea, but gets very complex very quickly (if one makes
> more than a trivial number of changes).

True. Perhaps a better idea, for those interested in absolute
backwards compatibility, is a (standard) method to keep the old
package versions lying around with standardised filenames (say,
siunitx-20080823.sty) that can be loaded when necessary.

Lance Carnes wrote about this sort of thing in an editorial in the
most recent PracTeX Journal. So I guess there must be *some* need for
it...

Will