Issue 1179: Sum.__str__() and Sum.doit with no explicit limits fails
http://code.google.com/p/sympy/issues/detail?id=1179
Comment #2 by andy.terrel:
opps I should have run some test on that bug fix (I deleted the last
comment). My two minute fix would just cover up problems instead of fix
them.
Its more broken than just that:
In [16]: s = Sum(f(i,k),(i,0,5),(k,0,2))
In [17]: s
Out[17]: Sum(f(i, k), (i, 0, 5))
But then digging deeper into the code it seems that Sum.doit can't handle
unbound functions.
In [2]: s = Sum(cos(z),z)
In [3]: s.doit()
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/usr/local/src/<ipython console> in <module>()
/usr/local/src/sympy/sympy/concrete/summations.py in doit(self, **hints)
66 # return self
67 f = self.function
---> 68 for i, a, b in self.limits:
69 f = eval_sum(f, (i, a, b))
70 if f is None:
TypeError: 'Symbol' object is not iterable
This should work exactly like Integrals but for some reason the code is a
lot different for the two. I would say that this points out that Sum needs
to be refactored, and possibly Integral.
Does anyone know what a limit with only 2 arguments is suppose to be? For
example:
In [5]: s = Sum(cos(z),(z,1))
In [6]: s
Out[6]: Sum(cos(z), (z, 1))
In [7]: s.doit()
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/usr/local/src/<ipython console> in <module>()
/usr/local/src/sympy/sympy/concrete/summations.py in doit(self, **hints)
66 # return self
67 f = self.function
---> 68 for i, a, b in self.limits:
69 f = eval_sum(f, (i, a, b))
70 if f is None:
ValueError: need more than 2 values to unpack
And then there is the need to fix when the limit is an equality....
-- Andy
Issue attribute updates:
Summary: Sum.__str__() and Sum.doit with no explicit limits fails
Status: Accepted
Labels: -NeedsReview
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