Updates:
Status: Started
Cc: andy.terrel
Comment #1 on issue 1566 by asmeurer: Allow Integral to be evaluated at
only an upper limit
http://code.google.com/p/sympy/issues/detail?id=1566
I fixed this by modifying _eval_interval(self, a, b) in Basic to evaluate
-self(a) if b is None or self(b) if a is None.
Integral uses this method, so it now works. I also modified the printer so
that it doesn't print a limit if it is None.
You get the behavior just by doing Integral(x**2, (x, None, 1)), which will
return 1/3 (the integral evaluated at
only the upper limit of 1. You can also only evaluate at the lower limit,
for the sake of completeness, so
Integral(x*82, (x, 1, None)) will return -1/3.
I will include this with my Google Summer of Code ODEs patch in a few
weeks, because I need this behavior for
my project anyway. If you want to look at it now, you can pull from
http://github.com/asmeurer/sympy/tree/odes (see commit 2f1d0b4).
The only class other than Basic that implements _eval_interval() is
Piecewise, and I was not able to figure out how
it works to make it do the same thing. It might break if you ever try to
evaluate only one limit on a Piecewise
integral, so Andy, could you possibly give me a pointer as to how to fix
this.
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