Bug introduced in 10.0 and fixed in 10.1

Why is the variable a ending up assigned to {1,2,3} after executing

  • 4
    $\begingroup$ What version are you using? I've tried this on Windows M9 and M10 and don't see the issue. $\endgroup$
    – Andy Ross
    Nov 19, 2014 at 3:23
  • $\begingroup$ I am using Mathematica 10 in OS X Yosemite. $\endgroup$ Nov 19, 2014 at 5:38
  • $\begingroup$ I cannot reproduce this in M10.0.1.0 on OS X 10.9.5 $\endgroup$ Nov 19, 2014 at 6:31
  • $\begingroup$ I can reproduce this on "10.0 for Mac OS X x86 (64-bit) (September 10, 2014)" using OS X Yosemite. Must be a platform-specific bug. You should report it to WRI. $\endgroup$
    – Andy Ross
    Nov 19, 2014 at 14:52
  • $\begingroup$ @MichaelE2 It's not. One more problem caused by the Suggestions Bar. $\endgroup$
    – Szabolcs
    Feb 17, 2015 at 20:37

2 Answers 2


This is yet another bug caused by the Suggestions Bar.


  • Go to Preferences... -> Interface, and uncheck "Show Suggestions Bar after last output".

I can reproduce it on OS X, Mathematica 10.0.2, but not in version 9.0.1.

Whenever I see that some people can reproduce a bug, some can't, I turn on the Suggestion Bar and check if it's the culprit. Very often it is. That's why I keep it off.

  • 2
    $\begingroup$ A-ha! I turned off the Suggestions Bar long ago as soon as I found out that I could. I did not realize it also had such a side effect. Its popping in and out of existence is enough of a headache for me. +1 $\endgroup$
    – Michael E2
    Feb 17, 2015 at 22:07

Very strange!

If you put an "a" after it works as expected:

Module[{a}, a = Range[3];

It also works if you suppress the Module's output (but not ListPlot's):

Module[{a}, a = Range[3];
  • 1
    $\begingroup$ This is yet another symptom of Sugestions Bar caused trouble. Putting the a at the end prevents the Suggestions Bar from messing with the previous output. $\endgroup$
    – Szabolcs
    Feb 17, 2015 at 20:38

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