[Python-Dev] Re: [Python-checkins] CVS: python/dist/src/Objects object.c,2.107,2.108

2001年1月19日 09:44:50 -0500 (EST)

>>>>> "GvR" == Guido van Rossum <gvanrossum@users.sourceforge.net> writes:

 GvR> Log Message: Changes to recursive-object comparisons, having to
 GvR> do with a test case I found where rich comparison of unequal
 GvR> recursive objects gave unintuituve results. In a discussion
 GvR> with Tim, where we discovered that our intuition on when a<=b
 GvR> should be true was failing, we decided to outlaw ordering
 GvR> comparisons on recursive objects. (Once we have fixed our
 GvR> intuition and designed a matching algorithm that's practical
 GvR> and reasonable to implement, we can allow such orderings
 GvR> again.)
Sounds sensible to me! I was quite puzzled about what <= should
return for recursive objects.
 GvR> - Changed the nesting limit to a more reasonable small 20; this
 GvR> only slows down comparisons of very deeply nested objects
 GvR> (unlikely to occur in practice), while speeding up
 GvR> comparisons of recursive objects (previously, this would
 GvR> first waste time and space on 500 nested comparisons before
 GvR> it would start detecting recursion).
After we talked through this code yesterday, I was also thinking that
the limit was too high :-).
Jeremy