[Travis]I obviously don't understand the intricacies here, so fortunately it's not a key issue for me because I'm not betting the farm on being able to inherit from the arrayobject. But, it is apparent that I don't understand all the issues.
I appreciate some of what Paul is saying here, but I'm not fully
convinced that this is still true with Python 2.2 and up new-style
c-types. The concerns seem to be over the fact that you have to
re-implement everything in the sub-class because the base-class will
always return one of its objects instead of a sub-class object.
It seems to me, however, that if the C methods use the object type
alloc function when creating new objects then some of this problem is
avoided (i.e. if the method is called with a sub-class type passed in,
then a sub-class type gets set).
This would severely constrain the __new__ method of the subclass.
The only reason I'm thinking of here is to have it inherit from the C-array many of the default methods without having to implement them all itself. I think Paul is saying that this never works with C-types like arrays, and I guess from your comments you agree with him.Have you looked at how Python now allows sub-classing in C? I'm not an expert here, but it seems like a lot of the problems you were discussing have been ameliorated. There are probably still issues, but....
I will know more when I seen what happens with a Matrix Object
inheriting from a Python C-array object.
And why would a Matrix need to inherit from a C-array? Wouldn't it
make more sense from an OO POV for the Matrix to *have* a C-array
without *being* one?
The only real reason for wanting to construct a separate Matrix object is the need to overload the * operation to do matrix multiplication instead of element-by-element multiplication.
-Travis
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