Comment #4 on issue 2068 by asmeurer: integrate(Integral(f(x), x), x) fails
http://code.google.com/p/sympy/issues/detail?id=2068
Because of the fix at https://github.com/sympy/sympy/pull/7, this is now
failing with a different error:
In [1]: integrate(Integral(f(x), x), x)
...:
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/Users/aaronmeurer/Documents/Python/sympy/sympy/<ipython console> in
<module>()
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/utilities/decorator.pyc
in
threaded_decorator(expr, *args, **kwargs)
54 return Add(*[ func(f, *args, **kwargs) for f in
expr.args ])
55 else:
---> 56 return func(expr, *args, **kwargs)
57
58 threaded_decorator.__doc__ = func.__doc__
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/integrals/integrals.py
in
integrate(*args, **kwargs)
554
555 if isinstance(integral, Integral):
--> 556 return integral.doit(deep = False)
557 else:
558 return integral
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/integrals/integrals.py
in
doit(self, **hints)
165 for lim in self.limits:
166 x = lim[0]
--> 167 antideriv = self._eval_integral(function, x)
168
169 if antideriv is None:
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/integrals/integrals.py
in
_eval_integral(self, f, x)
363
364 # fall back to the more general algorithm
--> 365 h = heurisch(g, x, hints=[])
366
367 # if we failed maybe it was because we had
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/integrals/risch.pyc
in heurisch(f, x, **kwargs)
277
278 s = u_split[0] * Mul(*[ k for k, v in special.iteritems() if v
])
--> 279 a, b, c = [ p.as_poly(*V).total_degree() for p in [s, P, Q] ]
280
281 poly_denom = (s * v_split[0] * deflation(v_split[1])).as_basic()
AttributeError: 'NoneType' object has no attribute 'total_degree'
Which is because heurisch() doesn't know how to handle Integral objects.
We need to put in a hook in Integral.__new__ and in integrate() to convert
an Integral argument into a single multiple Integral in the first case, or
else something that calls doit() and evaluates if it works or else creates
an multiple Integral in the second case.
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