Python has a module named abc for implementing "abstract base classes", see http://www.python.org/dev/peps/pep-3119/ for definitions and usage. Why is it not used in Sage ?
Example: if type(i) is 'int', isinstance (i, Integer) should be True (today it's False).
One reason is that abstract base classes are relatively new (Python 2.6) and the work hasn't been done to put them in place. It will require a bit of thought about how best to use them within Sage. For example, I don't think we want isinstance(i, Integer) to be True since in Sage Integer is a concrete class wrapping an MPIR mpz_t. However, you could register Integer as numbers.Integral and then test against that.
So, it seems that in many situations we have to code if isinstance (n, (int, Integer)) instead of if isinstance (n, Integer), despite the fact that the latter is much more natural. Sigh.
Right now, isinstance (n,Integer) is used to check whether Cython code can directly access the wrapped gmp integer. Changing this would just move the instance checks around, but not really simplify anything.
Asked: 2011-09-30 14:12:06 +0100
Seen: 521 times
Last updated: Oct 01 '11
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