Thanks for the help, but I'm still stuck!
> create GeneratingFunction.__new__() with your own arguments and then
> call Poly.__new__() from it, with any preprocessing that you need.
This is what I've got so far:
====== generating_functions.py ========
from sympy import Poly
X = Symbol('X')
class GeneratingFunction(Poly):
def __new__(cls,*coefficients,**kwargs):
normalization_factor = float(sum(coefficients))
if normalization_factor: normalized_coefficients = tuple(map
(lambda c: sympify(c / normalization_factor), coefficients))
else: normalized_coefficients = coefficients
monomials = tuple(map(lambda i: (i,),xrange(len(coefficients))))
gf = Poly.__new__(cls,zip
(normalized_coefficients,monomials),X,**kwargs)
gf.coefficients = normalized_coefficients
return gf
===== end generating_functions.py ======
>>> from generating_functions import GeneratingFunction
>>> gf = GeneratingFunction(10,4,4,2)
>>> gf = GeneratingFunction(10,4,4,2)
>>> gf(1)
1.00000000000000
>>> two_moment = gf * gf
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.5/site-packages/sympy/sympy/polys/
polynomial.py", line 952, in __mul__
self, poly = self.unify_with(other)
File "/usr/local/lib/python2.5/site-packages/sympy/sympy/polys/
polynomial.py", line 1525, in unify_with
other = cls(other, *symbols, **flags)
File "generating_functions.py", line 34, in __new__
normalization_factor = float(sum(coefficients))
File "/usr/local/lib/python2.5/site-packages/sympy/sympy/polys/
polynomial.py", line 867, in __add__
self, poly = self.unify_with(other)
File "/usr/local/lib/python2.5/site-packages/sympy/sympy/polys/
polynomial.py", line 1525, in unify_with
other = cls(other, *symbols, **flags)
File "generating_functions.py", line 34, in __new__
normalization_factor = float(sum(coefficients))
File "/usr/local/lib/python2.5/site-packages/sympy/sympy/core/
basic.py", line 1954, in __float__
raise ValueError("Symbolic value, can't compute")
ValueError: Symbolic value, can't compute
>>>
It seems that GeneratingFunction.__new__ is being called internally
with different arguments than I expect whenever arithmetic operations
are called.
> > Can I get the functionality I want by forcing
> > GeneratingFunction.__new__ to perform all the same checks and magic on
> > its argument that Poly.__new__ is already doing? Is there an easier
> > way?
It seems like the above is the only thing I can do! The Poly class
can be instantiated using a few different calling schemes (lists,
tuples, dictionaries, &c.) and I'm going to have to anticipate each
scheme and extract the parameters I want from it, all in
GeneratingFunction.__new__.
Is this correct?
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sympy" group.
To post to this group, send email to sympy@googlegroups.com
To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/sympy?hl=en
-~----------~----~----~----~------~----~------~--~---
