CODEWITHSUNDEEP
pythonsympy
M. Heuer
M. Heuer

Reputation: 407

sympy integration limits error: TypeError: bad operand type for unary -: 'tuple'

The following code

from sympy import *
r = Symbol('r', real=True, positive=True)
a = Symbol('a', real=True, positive=True)
Integral(1/r**2,(r,oo,a)).doit()

results in an error

TypeError: bad operand type for unary -: 'tuple'

whereas

-Integral(1/r**2,(r,a,oo)).doit()

, which is an equivalent formulation of the integral above, gives the correct result: -1/a.

Furthermore, lowering the restrictions for the domain of a

r = Symbol('r', real=True, positive=True)
a = Symbol('a')
Integral(1/r**2,(r,oo,a)).doit()

gives the correct result as well.

Is this a bug in sympy or what is going wrong here?

Edit: It is completely valid to integrate from Infinity to a positive value. Mathematica does the job right as I wrote in my comment addressed to @BenT.

Upvotes: 4

Views: 666

Answers (1)

M. Heuer
M. Heuer

Reputation: 407

I can confirm that this is a bug in sympy. I opened an issue in their github (https://github.com/sympy/sympy/issues/13536) which will be resolved soon.

Upvotes: 2

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