> To solve this I tried to write a wrapper for
> sage.rings.integer.Integer.__mul__ however I get the error "can't set
> attributes of built-in/extension type 'sage.rings.integer.Integer'"
> when executing
> sage: sage.rings.integer.Integer.__mul__ = my_new_multiplication
You're getting the error you're seeing because
sage.rings.integer.Integer isn't a regular Python class. It is a C
extension type for speed reasons. It is the same error you'd get if
you did "float.new_attribute = 5".
> Could someone enlighten me about either problem, and a possible way to
> fix it.
The problem you are having with your "MyFloat" class is more of a
Python problem than a Sage problem. I assume that you're inheriting
the multiplication method from float somewhat like this:
class MyFloat(float):
pass
The problem is that the multiplication routines in float don't know to
create an object of type MyFloat. Thus, if you do "3*MyFloat(2.0)" in
pure Python (no Sage integers involved), you'll get a value of 6.0
with a type of float. To fix this, you could define MyFloat in the
following way:
sage: class MyFloat(float):
....: def __mul__(self, x):
....: return MyFloat(float(self)*x)
....: def __rmul__(self, x):
....: return MyFloat(x*float(self))
Then, you get the following behavior which is what I assume you want:
sage: a = MyFloat(2)
sage: 3*a
6.0
sage: type(_)
<class '__main__.MyFloat'>
sage: a*3
6.0
sage: type(_)
<class '__main__.MyFloat'>
--Mike
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