Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 4132 by [email protected]: evaluating series() twice for a generic
function fails
http://code.google.com/p/sympy/issues/detail?id=4132
Here is the problem:
In [1]: from sympy import *
In [2]: f=Function("f")
In [3]: x=Symbol('x')
In [4]: a=Symbol('a')
In [5]: series(f(x),x,a)
Out[5]: f(a) + x*Subs(Derivative(f(_xi_1), _xi_1), (_xi_1,), (a,)) +
x**2*Subs(Derivative(f(_xi_1), _xi_1, _xi_1), (_xi_1,), (a,))/2 +
x**3*Subs(Derivative(f(_xi_1), _xi_1, _xi_1, _xi_1), (_xi_1,), (a,))/6 +
x**4*Subs(Derivative(f(_xi_1), _xi_1, _xi_1, _xi_1, _xi_1), (_xi_1,),
(a,))/24 + x**5*Subs(Derivative(f(_xi_1), _xi_1, _xi_1, _xi_1, _xi_1,
_xi_1), (_xi_1,), (a,))/120 + O(x**6)
In [6]: series(f(x),x,a)
Out[6]: f(a) + x*Subs(Derivative(f(_xi_1), _xi_1), (_xi_1,), (_x + a,)) +
O(x**6)
If I used a specific function, e.g. cos(x), the problem does not appear.
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