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Re: Mathematica 9: bug in merging cells

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  • Subject: [mg128948] Re: Mathematica 9: bug in merging cells
  • From: David Reiss <dbreiss at>
  • Date: Wed, 5 Dec 2012 03:13:18 -0500 (EST)
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  • References: <k9kekh$68c$>

Just a quick observation to note that one does not need the comment
between the first two code lines, the presence of a carriage return is
all that's needed to create the error upon merging the two cells.
Thus, the first cell would contain

a = 1;

b = 2;

and the second cell would have any code in it: e.g.,

c = 3;

Then merge the two and the error box appears.


On Dec 4, 4:09 am, Fred Simons <f.h.sim... 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 well.
> 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 this
> 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 the
> next line with another RowBox.
> During writing this message, I found that the same happens when you try
> to copy and paste the first cell.
> Fred Simons
> Eindhoven University of Technology

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