Comment #19 on issue 2571 by [email protected]: Regression in Integral.subs
http://code.google.com/p/sympy/issues/detail?id=2571
Regarding the nesting...that's where xreplace can be used where the
transform acts on all Integrals that are in the expression. If you look at
how Ronan implemented the xreplace for powdenest you will see a working
example.
As for my examples, I don't know why the commands to generate the output
didn't come through. I'm trying again. "Just do it if it works" doesn't
answer the question of "what did you mean"? For `Integral(x, (x,
x**2)).subs(x, y)` do you mean:
>>> integrate(y,(x,y**2))
y**3
>>> integrate(y,(x,x**2))
x**2*y
>>> integrate(x,(x,y**2))
y**4/2
Athough this is a cooked-up example, it demonstrates that there are several
different meanings for the subs so a criteria should be made so the user
knows what to expect. If we don't disallow the use of the integration
variable in the limits (like the TI calculator) then we need to think about
what is the most reasonable expectation. Things that can help us decide,
perhaps, are whether the integral is definite (3-arg limit), an evaluate-at
integral (two limits) or an indefinite integral (1-arg limit).
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