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MathGroup Archive 2000

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Re: User problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24007] Re: User problem
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 20 Jun 2000 03:07:26 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <8ihuik$lcl@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

you really change the loop variable inside a loop
random *and* you are wondering that the system
crashes ? What will a simple C program do when you
write

for(k=0; k<i;){
  i=random();
  randomArray[i]=i;
 }

The system crashes because Mathematica allocate for
Table[_,{i,1,n}] internal an array of length n-1. 
using a random number larger than n will overflow
the array and write something into memory used
by the system, the stack or what ever.

You mean

RandomTab[max_Integer:249] := 
  Table[Random[Integer, {1, 4}], {Random[Integer, max]}]

and you should write down it.

Regards
  Jens

joseph wrote:
> 
> Can anyone help:
> I am trying to contstruct a table of random integers
> between 1 and 4. I'd like to vary the number of
> elements in the table from time to time. The
> contruction that I use in Mathematica is as follows:
> 
> genome = Table[i = Random[Integer, {1, 4}], {i, 249}]
> 
> The problem with this is as follows: the above
> generates tables of varying length up to and including
> 249 elements.  However, when I try to generate any
> table containing more than 249 elements, I get the
> following error message on my screen:
> 
> This program has performed an illegal operation and
> will be shut down.  If the problem persists please
> contact the vendor.
> 
> I have version 4 of Mathematica, and am running it on
> a Windows98 platform (Dell NoteBook)
> 
> Any assistance will be greatly appreciated.
> 
> Joseph468 at yahoo.com
> 
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