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fmpz_poly_is_squarefree wrong results? #2084

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fingolfin opened this issue Oct 8, 2024 · 4 comments
Open

fmpz_poly_is_squarefree wrong results? #2084

fingolfin opened this issue Oct 8, 2024 · 4 comments

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@fingolfin
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It indicates that 4x is square-free, but that doesn't agree with its documentation, which states

Returns whether the polynomial poly is square-free. A non-zero polynomial is defined to be square-free if it has no non-unit square factors. We also define the zero polynomial to be square-free.

See also Nemocas/Nemo.jl#1742 and Nemocas/Nemo.jl#1311

@albinahlback
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A change to something like

Returns whether the polynomial poly is square-free. A non-zero polynomial is defined to be square-free if its factorisation contains no non-constant square factors. We also define the zero polynomial to be square-free.

would work, right?

@fingolfin
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Thank you. That would at least clarify that it deviates from the usual mathematical definition. Perhaps it could be made even more explicitly by in addition inserting something like this:

This differs somewhat from the usual definition, e.g. we consider the polynomial 4x in Z[x] as square-free.

@thofma
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thofma commented Oct 15, 2024

Or just write, that it returns whether poly is squarefree as a polynomial over the rationals.

@edgarcosta
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That or just say it doesn't double roots over the complex numbers

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