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Re: Re: why no result & no error from this recursion

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82463] Re: [mg82431] Re: [mg82403] why no result & no error from this recursion
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Sat, 20 Oct 2007 22:15:30 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200710190904.FAA05304@smc.vnet.net> <200710200949.FAA28706@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

The evaluation ended rather quickly, and the front end was immediately 
ready for the next input.

But I've now verified that the kernel definitely quit.  At least that's 
what I surmise by going to Evaluation -> Quit Kernel and seeing that the 
Local kernel was grayed out, indicating it was no longer running.



Sseziwa Mukasa wrote:
> On Oct 19, 2007, at 5:04 AM, Murray Eisenberg wrote:
> 
>> Why does the following recursion produce neither a result nor an error
>> message -- nor a system crash?
>>
>> Block[{$RecursionLimit=50002}, (If[#<1, "", "." <> #0[# - 1]] &) 
>> [50000]]
>>
>> I even tried setting $RecursionLimit=Infinity, but no change.
>>
>> I presume this is just bumping up against a hardware/OS limit, so I'm
>> surprised to get no error message and no crash.
> 
> My guess is that the front end is having problems formatting 50000  
> '.' for display.  I've noticed sometimes that calculations that  
> generate long strings on output can appear to have hung but the  
> kernel has not crashed and the front end is unresponsive.
> 
> Regards,
> 
> Ssezi
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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