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math/big: Typo in the documentation of Int.DivMod #13875

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TomCoates8161 opened this issue Jan 8, 2016 · 4 comments
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math/big: Typo in the documentation of Int.DivMod #13875

TomCoates8161 opened this issue Jan 8, 2016 · 4 comments
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Documentation FrozenDueToAge
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Go1.6Maybe

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@TomCoates8161
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The documentation for DivMod, in the big library, suggests that z.DivMod(x,y,w) sets z to the quotient q and w to the modulus m, where q and m satisfy

m = x - y*q with 0 <= m < |q|

I believe that this should read

m = x - y*q with 0 <= m < |y|

so that it agrees with the reference mentioned in the documentation for DivMod: Raymond T. Boute, “The Euclidean definition of the functions div and mod”. ACM Transactions on Programming Languages and Systems (TOPLAS), 14(2):127-144, New York, NY, USA, 4/1992. ACM press.
@TomCoates8161 TomCoates8161 changed the title mistake in the definition of DivMod math/big: mistake in the definition of DivMod Jan 8, 2016
@ianlancetaylor
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I can't tell: is this a problem with the docs, or a problem with the code?

@TomCoates8161
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Code looks OK to me.

@ianlancetaylor ianlancetaylor added this to the Go1.6Maybe milestone Jan 8, 2016
@rsc
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rsc commented Jan 8, 2016

Yes, if the operation is q=x/y then clearly the remainder (sorry, modulus) must be < y, not < q. Thanks.

@griesemer griesemer changed the title math/big: mistake in the definition of DivMod math/big: Typo in the documentation of Int.DivMod Jan 8, 2016
@gopherbot
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CL https://golang.org/cl/18441 mentions this issue.

@golang golang locked and limited conversation to collaborators Jan 7, 2017
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