Sage can use the symbolic ring to create formal sums and products of
variables. I would like to make my own objects (with some extra
attributes and methods) behave like these without reimplementing the
distributive law, etc. For example this would work if they could be
part of sage Expressions which I could then retrieve using
Expression.operands(). I would like to do something like this:
sage: a = myVar("a", "some data about a")
sage: b = myVar("b", "foo")
sage: p = ((a+b)^2).expand()
a^2 + 2*a*b + b^2
sage: p.operands()[0]
a^2
sage: p.operands()[0].operands()[0]
a
sage: _.get_data()
"some data about a"
I tried using something like
sage: a = SR._force_pyobject(myInstance)
but then there is an error when I try to use a in an expression
because the operators aren't defined for my class. I could use a
dictionary with traditional variables as keys, but this is awkward
because there isn't a natural place for the dictionary to be if I am
passing these things to functions, etc. and also because I sometimes
want two variables with the same name but different extra data. I
also looked at subclassing Expression, but that didn't seem to work
either. Any ideas? Is there a more natural way to do something like
this?
Thanks!
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