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Re: behavior from Mathematica 7 to Mathematica 8

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114019] Re: behavior from Mathematica 7 to Mathematica 8
  • From: David Skulsky <edskulsky at gmail.com>
  • Date: Sat, 20 Nov 2010 18:25:59 -0500 (EST)
  • References: <ic8ab4$7ve$1@smc.vnet.net>

On Nov 20, 3:10 am, Bill Rowe <readn... at sbcglobal.net> wrote:
> On 11/19/10 at 5:10 AM, edskul... at gmail.com (David Skulsky) wrote:
>
> >While testing Mathematica 8 on some heritage code, I found a problem
> >which a colleague traced to a behavioral change in Times[].
> >Specifically, the documentation for Times[] states that "0 x
> >evaluates to 0, but 0.0 x is left unchanged."  This appears to be
> >true in Mathematica 7 but not in Mathematica 8 (at least not under
> >Mac OS X 10.6.4).
> >I have informed Wolfram about this change (bug?).
>
> I can confirm getting 0. as the result of doing 0.0 x in version
> 8 but getting 0.x as the result in version 7. It seems to me the
> result returned by version 8 is more consistent and version 8 is
> correcting a "bug" that was present in version 7.

I'm not sure what Times[] should do, but I can say that this change
resulted in a problem for me in M8 that wasn't present in M7.  What I
do know, however, is that the documentation is incorrect.
Furthermore, it seems to imply that the behavior in M7 was intentional
(or at least that it was recognized and not identified as a bug).

Most importantly, Times[] is a fundamental function in Mathematica and
extraordinary care should be taken before any changes to such
functions are made. If changes are made, they should be properly
documented and shouted from the rooftops because it's likely that they
will affect a large fraction of the Mathematica community.

David Skulsky


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