Updates:
Status: Accepted
Labels: -NeedsReview -asmeurer -Milestone-Release0.7.0
Milestone-Release0.7.1
Comment #22 on issue 1525 by asmeurer: No integration by substitution
http://code.google.com/p/sympy/issues/detail?id=1525
This was pushed in.
I think I'll leave this to be about f(g(x)).diff(x) not working:
In [1]: f(g(x)).diff(x)
---------------------------------------------------------------------------
NotImplementedError Traceback (most recent call last)
/Users/aaronmeurer/Documents/python/sympy/sympy/<ipython console> in
<module>()
/Users/aaronmeurer/Documents/python/sympy/sympy/sympy/core/expr.py in
diff(self, *symbols, **assumptions)
1614 new_symbols = map(sympify, symbols) # e.g. x, 2, y, z
1615 assumptions.setdefault("evaluate", True)
-> 1616 return Derivative(self, *new_symbols, **assumptions)
1617
1618
###########################################################################
/Users/aaronmeurer/Documents/python/sympy/sympy/sympy/core/function.py in
__new__(cls, expr, *symbols, **assumptions)
652 unevaluated_symbols = []
653 for s in symbolgen:
--> 654 obj = expr._eval_derivative(s)
655 if obj is None:
656 unevaluated_symbols.append(s)
/Users/aaronmeurer/Documents/python/sympy/sympy/sympy/core/function.py in
_eval_derivative(self, s)
249 continue
250 if isinstance(self.func, FunctionClass):
--> 251 df = self.fdiff(i)
252 l.append(df * da)
253 return Add(*l)
/Users/aaronmeurer/Documents/python/sympy/sympy/sympy/core/function.py in
fdiff(self, argindex)
496 if not self.args[argindex-1].is_Symbol:
497 # See issue 1525 and issue 1620
--> 498 raise NotImplementedError("Cannot express derivatives
evaluated at a point")
499 return Derivative(self,self.args[argindex-1],evaluate=False)
500
NotImplementedError: Cannot express derivatives evaluated at a point
There are XFAILed tests in sympy/core/tests/test_function.py relating to
this.
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