code review 155010043: math/big: Allow non-prime modulus for ModInverse

math/big: Allow non-prime modulus for ModInverse

The inverse is defined whenever the element and the
modulus are relatively prime.  The code already handles
this situation, but the spec does not.

Test that it does indeed work.

Fixes issue 8875

[khr, 2014-10-06 22:25:13]

Hello agl@golang.org (cc: golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://khr%40golang.org@code.google.com/p/go/

[khr, 2014-10-13 20:48:47]

On 2014/10/06 22:25:13, khr wrote:
> Hello mailto:agl@golang.org (cc: mailto:golang-codereviews@googlegroups.com),
> 
> I'd like you to review this change to
> https://khr%40golang.org@code.google.com/p/go/

Ping.

[agl1, 2014-10-13 21:05:31]

Sorry, had drafts but forgot to hit publish.

https://codereview.appspot.com/155010043/diff/40001/src/math/big/int.go
File src/math/big/int.go (right):

https://codereview.appspot.com/155010043/diff/40001/src/math/big/int.go#newco...
src/math/big/int.go:756: // and returns z.  g and n must be relatively prime.
only one space after a period in this package.

Sentences should start with a capital letter. What about "The arguments g and n
must be relatively prime or the result is undefined."

[khr, 2014-10-13 21:15:33]

On 2014/10/13 21:05:31, agl1 wrote:
> Sorry, had drafts but forgot to hit publish.
> 
> https://codereview.appspot.com/155010043/diff/40001/src/math/big/int.go
> File src/math/big/int.go (right):
> 
>
https://codereview.appspot.com/155010043/diff/40001/src/math/big/int.go#newco...
> src/math/big/int.go:756: // and returns z.  g and n must be relatively prime.
> only one space after a period in this package.
> 
> Sentences should start with a capital letter. What about "The arguments g and
n
> must be relatively prime or the result is undefined."

How about "If g and n are not relatively prime, the result is undefined."  It
matches the undefined language in, e.g., Int64().

[agl1, 2014-10-14 01:32:32]

LGTM

[khr, 2014-10-14 21:09:59]

*** Submitted as https://code.google.com/p/go/source/detail?r=9825b678db2f ***

math/big: Allow non-prime modulus for ModInverse

The inverse is defined whenever the element and the
modulus are relatively prime.  The code already handles
this situation, but the spec does not.

Test that it does indeed work.

Fixes issue 8875

LGTM=agl
R=agl
CC=golang-codereviews
https://codereview.appspot.com/155010043

[gobot, 2014-10-14 21:14:30]

This CL appears to have broken the android-arm-crawshaw builder.
See http://build.golang.org/log/981e654bbf5fcce3d6060234fa421d956c4455ad