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Re: Re-virginating Manipulates?

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  • Subject: [mg114432] Re: Re-virginating Manipulates?
  • From: John Fultz <jfultz at>
  • Date: Sat, 4 Dec 2010 06:13:48 -0500 (EST)

On Fri, 3 Dec 2010 05:19:57 -0500 (EST), AES wrote:
>> In the Cell menu, "Delete All Output" will get rid of all of the
>> output, print, and message cells, which goes a long way toward what
>> you want.  Of course, there may be latent kernel state which you'll
>> need to flush.  And the only absolutely sure way of doing that is to
>> quit the kernel.  Evaluation->Quit Kernel->Local will do it, or you
>> can just evaluate
>> Quit
>> in a new cell.
>> Sincerely,
>> John Fultz
> Thanks much.
> As I'm sure you know, some apps have a Revert command (often in the same
> menu as their Save and Open commands), which generally means "Revert to
> last Saved version" and which can be handy -- but of course this applies
> only to documents, not the app itself; and it can be dangerous in the
> case of apps that periodically do auto-Saves on docs without visible
> indication to the user.
> It's always surprised me, frankly, that Mathematica doesn't have a
> built-in "Clean Slate" facility for its kernel that would be equivalent
> to executing a "Quit Kernel, then Restart Kernel" command (although
> there was a third party (?) command or utility with this name in some
> earlier version, was there not?).  Must be somehow hard to do this?

Todd Gayley wrote a utility called CleanSlate.  He also wrote an entire article
for the Mathematica Journal about how he did it (this was, I think, in 1994 or
1995).  I don't remember the details, but it turned out that it was definitely
not trivial.  It's easy enough to clear out the Global` namespace, which is
satisfactory enough for many purposes.  But to truly reset the kernel to a
virgin state is a much more challenging problem.

I'm not sure whether CleanSlate is still around or not, or how well it still
works.  Others on this list probably know better than I.

That having been said, it really is very easy to quit and restart your kernel. 
It takes almost no time on modern computers.  And there won't be any weirdo bugs
in corner cases of things that were overlooked in the "virgination".


John Fultz
jfultz at
User Interface Group
Wolfram Research, Inc.

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