#14437: rsolve fails with initial conditions
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Reporter: zimmerma | Owner: burcin
Type: defect | Status: new
Priority: minor | Milestone: sage-5.10
Component: calculus | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by kcrisman):
This is a pure Sympy question.
{{{
In [1]: import sympy
In [3]: u = sympy.Function('u')
In [5]: n = sympy.Symbol('n',integer=True)
In [6]: f = u(n+2) - u(n+1) + u(n)/4
In [7]: sympy.rsolve(f,u(n))
Out[7]: 2**(-n)*C0*RisingFactorial(C0/C1 + 1, n)/RisingFactorial(C0/C1, n)
In [8]: sympy.rsolve(f,u(n),{u(0):0,u(1):1})
In [9]:
}}}
I guess you could report it [http://code.google.com/p/sympy/issues/list
upstream] and we could verify a fix here eventually.
Second, the object you did is a Sympy object, so you would want to
translate it to Sage first.
{{{
sage: sage: rsolve(f,u(n))
2**(-n)*C0*RisingFactorial(C0/C1 + 1, n)/RisingFactorial(C0/C1, n)
sage: _._sage_()
AttributeError: 'RisingFactorial' object has no attribute '_sage_'
}}}
But separately, it would be nice, true, to have a good translation of
!RisingFactorial. I suggest you split this up into two different tickets,
if that's okay, as the issues are quite different.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14437#comment:1>
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