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Re: Mathematica 9: bug in merging cells

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  • Subject: [mg128941] Re: Mathematica 9: bug in merging cells
  • From: Murray Eisenberg <murray at>
  • Date: Wed, 5 Dec 2012 03:10:57 -0500 (EST)
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I'm seeing exactly the same cell-merge bug in Mathematica 9 under OS X 

It has nothing to do with the (* comment *) per se. Exactly the same 
thing happens if in the first cell you replace the comment line with a 
blank line.

On the other hand, I don't get any error with copy-and-paste, whether 
with the (* comment *) or with just a blank line there.

On Dec 4, 2012, at 4:14 AM, Fred Simons <f.h.simons at> wrote:

> When writing a larger program, I usually test the single steps in
> separate cells, then merge these cells and localize the variables by

> wrapping the contents of the merged cells in a Module. By doing so in

> Mathematica 9, due to a bug in merging cells, I lost a lot of code. I

> reported this bug to WRI two weeks ago. It is not yet repaired in the

> new release, so I thought I would mention this annoying bug here as 
> This is an example (Mathematica 9 for Windows, I am not aware if this

> happens for other systems too).
> Construct two input cells, the first one containing
> a=1;
> (* comment *)
> b=2;
> and the second one
> c=3;
> When merging these two cells the contents ending with the comment is

> shown in an orange rectangle, with the error message that there is a

> RowBox with an invalid first argument. I cannot see any reason why 
> merging of cells could not be undone with ctrl-Z, but it cannot and
> therefore part of my code was gone.
> In this simple example I could see how to fix it. Toggle ctrl-E for
> seeing the box structure. Place a } just behind the RowBox with the
> comment  and a { behind the very first RowBox[, that is followed on 
> next line with another RowBox.
> During writing this message, I found that the same happens when you 
> to copy and paste the first cell.
> Fred Simons
> Eindhoven University of Technology

Murray Eisenberg                                    
murray at
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Lederle Graduate Research Tower            phone 413 549-1020 (H)
University of Massachusetts                               413 545-2838 
710 North Pleasant Street                         fax   413 545-1801
Amherst, MA 01003-9305

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