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Re: Mod and QuotientRemainder are inconsistent

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124866] Re: Mod and QuotientRemainder are inconsistent
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Fri, 10 Feb 2012 05:51:52 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201202091035.FAA18248@smc.vnet.net>

Note also that:

Mod[12, 0.1, 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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