Am 11.03.2012 22:48, schrieb Aaron Meurer:
IOW fully general double dispatch means you have to think about and fill out
ALL cells in the matrix.
Which means that the matrix cannot be extended in more than one direction
independently.
Right, we have to accept that there will be certain combinations that
are undefined with this, because of conflicting rules. That's
actually an important consideration, and one of the reasons that I
wanted to make that wiki page that lists everything. FWIW, I think
that undefined combinations should remain just that, undefined, i.e.,
they can return anything within the constructs of either definition.
In that case you'd have to check that both constructs Do The Right Thing.
Otherwise, changes somewhere up the hierarchy might make any unit test
that uses subclasses fail.
I'd suggest making the undefined matrix cells truly undefined, i.e.
calling them throws an error. That forces whoever integrates two type
hierarchies to make sure that the combinations are correct (probably by
contacting the authors of the extensions and work the combination out).
Counter-question: Do we actually do code coverage analysis?
Yes. See the bin/coverage_report.py script. Thanks to the work of
people like Chris, and many of our GCI students, we actually have
pretty good coverage right now.
Ah, sweet. I wasn't aware of that.
- Code can be much simpler if the rules follow some kind of pattern,
because you can then just code the pattern. You might say that that's
also possible with data, but then you are just doing things in code
anyway, but in a more circuitous way.
Patterns can be factored out in code just as in data.
No, I meant that patterns can be factored out only in code, not in
data. Because you have the full power of programmability when you do
things in code, whereas data will be limited to whatever level of
power you give it
More power also means more potential for unexpected side effects.
I still stand by my words.
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