On 2005 Jan 10, at 23:19, Phillip J. Eby wrote: ...
As I said, after more thought, I'm actually less concerned about the performance than I am about even remotely encouraging the combination of Liskov violation *and* concrete adaptation
As per other msg, abstract classes have just the same issues as concrete ones.
If Ka-Ping Yee's idea (per Artima cmts on BDFL blog) of having interfaces supply template methods too ever flies, the issue would arise there, too (a BDFL comment with a -1 suggests it won't fly, though).
targets. But, if "after the dust settles" it turns out this is going to be supported after all, then we can worry about the performance if need be.
Note, however, that your statements actually support the idea of *not* adding a special case for Liskov violators. If newer code uses interfaces, the Liskov-violation mechanism is useless. If older code doesn't have __conform__, it cannot possibly *use* the Liskov-violation mechanism.
Adding __conform__ to a class to raise a LiskovViolation when needed is a TINY change compared to the refactoring needed to use template-methods without subclassing.
Alex
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