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Topic: Mod and QuotientRemainder are inconsistent
Replies: 2   Last Post: Feb 10, 2012 6:02 AM

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Andrzej Kozlowski

Posts: 2,112
Registered: 1/29/05
Re: Mod and QuotientRemainder are inconsistent
Posted: Feb 10, 2012 5:52 AM
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Note also that:

Mod[12, 0.1, 1]


etc., which suggest to me that the result for Mod[12,0.1] must be a bug.

Andrzej Kozlowski

On 9 Feb 2012, at 11:35, Szabolcs wrote:

> Mod[12, 0.1] gives 0.1 despite 120*0.1 = 12. I expect this is because 0.1 is not representable in binary.
> QuotientRemainder[12, 0.1] gives {120, 0.} however, which is inconsistent with the result above.
> Quotient[12,0.1] gives 120 which is also inconsistent with Mod.
> Is this a bug or is it by design? It seems it is not safe to assume that
> QuotientRemainder[a,b] = {Quotient[a,b], Mod[a,b]}
> or that
> Quotient[a,b]*b + Mod[a,b] = a

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