JuliaApproximation / JuliaApproximation/ApproxFun.jl
Multiple Integrals give different results
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Description
So I'm doing iterated integrals and there is something funky when I composite them
So for example
Evaluation(Chebyshev(), -1)*Derivative(Chebyshev(),1)*Integral(Chebyshev(), 1) - Evaluation(Chebyshev(), -1)
Gives me the 0 vector, however
(Evaluation(Chebyshev(), -1)*Derivative(Chebyshev(),1)*Integral(Chebyshev(), 1))*Integral(Chebyshev(), 1)*Integral(Chebyshev(), 1) - Evaluation(Chebyshev(), -1)*Integral(Chebyshev(), 2)
Does not give me the 0 vector, I get
PlusOperator : Chebyshev() → ConstantSpace(Point(-1)) 0.0 0.125 2.77556e-17 -0.125 3.46945e-18 -1.73472e-17 2.1684e-17 -4.33681e-19 6.72205e-18 4.77049e-18 ⋯
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Research direction
Start by reproducing the two iterated-integral expressions from the issue and compare their results. Trace the implementation of composition, multiplication, differentiation, and integration to identify where equivalent expressions diverge. Done means both expressions produce the expected zero vector, with a regression test covering the discrepancy.
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Assessment
- Tech stack
- julia
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100