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Re: Re: Re: Can't abort a loop with Print inside (V6)

  • To: mathgroup at
  • Subject: [mg83146] Re: [mg83119] Re: [mg83089] Re: Can't abort a loop with Print inside (V6)
  • From: DrMajorBob <drmajorbob at>
  • Date: Tue, 13 Nov 2007 03:34:50 -0500 (EST)
  • References: <> <2230479.1194878974881.JavaMail.root@m35>
  • Reply-to: drmajorbob at

The KERNEL is finished with the loop before you can abort it; the  
front-end is still busy with outputs.

Even so, I think the outputs should stop as well.


On Mon, 12 Nov 2007 04:09:27 -0600, Bo Hu <bhu at> wrote:

> This is not about a loop running faster than one could stop it before
> it ends.  The simple loop runs for quite a few seconds on my Macbook
> Pro, because of the Print statement.  It appears to be improper
> synchronization between the kernel and the front end.  More like a
> misfeature if that's the intended behavior.
> Frank
> On Nov 10, 2007, at 3:42 AM, Bill Rowe wrote:
>> On 11/9/07 at 5:15 AM, frank1998 at (Frank Hu) wrote:
>>> It seems in Version 6 one can't abort  a loop if there's a Print
>>> statement inside.  Try the following code
>>> For[i = 1, i < 1000, ++i, Print[i]]
>>> No matter doing it from the menu or with the keyboard shortcut, the
>>> abort action will be ignored.  Under 5.2, the code stops right away
>>> when I hit Cmd-.
>>> Sometime, trying to abort would even freeze the whole program,
>>> causing lost sessions.  I'm running on Mac OS X
>>> 10.4.10. Any suggestions of what's going on?  Is this a bug or
>>> a new feature?
>> It would be better described as a feature than a bug. But the
>> "feature" is really nothing more than improved performance of
>> version 6 compared to previous versions rather than an intent to
>> prevent stopping a loop using Cmd-.
>> For any software (assuming good performance) it will be always
>> possible to write a loop that runs so fast that it simply cannot
>> be halted using the key sequence. This is a result of only
>> having a simple Print statement in the loop rather than having a
>> more complex loop.
>> For example, the loop
>> Do[Pause[1];Print[n],{n,100}]
>> can easily be halted with the Cmd-. key shortcut.
>> OTOH,
>> Do[Print[n],{n,100}]
>> cannot be halted in the same manner.
>> --
>> To reply via email subtract one hundred and four


DrMajorBob at

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