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reduce() for fraction field elements

asked 2022-01-28 17:06:38 +0200

AShah gravatar image

updated 2022-01-29 09:22:49 +0200

slelievre gravatar image

I am having an issue with the reduce() method for FractionFieldElement. In a Jupyter notebook I executed the following code

sage: S = FractionField(QQ['t'])
sage: S.inject_variables()
sage: R = PolynomialRing(FractionField(QQ['t']),'x',3)
sage: R.inject_variables()
sage: (((x0^2-x1^2)/(x0-x1)).reduce())

but this returned an object with NoneType, rather than a fraction field element or ring element. What am I doing wrong?

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answered 2022-01-28 23:35:02 +0200

rburing gravatar image

updated 2022-01-28 23:38:37 +0200

See the documentation of reduce: it modifies the element instead of returning a new copy. So:

sage: f = (x0^2-x1^2)/(x0-x1)
sage: f.reduce()
sage: f
x0 + x1

Also read in the documentation:

Automatically called for exact rings, but because it may be numerically unstable for inexact rings it must be called manually in that case.

So there is no point in calling it in your particular case.

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Asked: 2022-01-28 17:06:38 +0200

Seen: 36 times

Last updated: Jan 29