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MathGroup Archive 1990

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No Bug found...

  • To: mathgroup at yoda.ncsa.uiuc.edu
  • Subject: No Bug found...
  • From: uunet!decide!bobk (Bob Korsan)
  • Date: Wed, 15 Aug 90 10:54:30 PDT

You write:

----- Begin Included Message -----

>From saxony!uunet!yoda.ncsa.uiuc.edu!mathgroup-adm Tue Aug 14 20:59:46 1990
From: uunet!phobos.mathcs.carleton.edu!johnsonj
To: mathgroup at yoda.ncsa.uiuc.edu
Subject: Is N[10^-11,16] = a. 99999999999999e-12 a known bug?

There is a curious bug in the N[] function, involving (as far as I can tell)
only calculations at sixteen decimal places.  I did a quick check with

  Table[Table[{i, j, N[10^-i, j]}, {j, 1, 2 * i}], {i, 1, 50}]

and got errors for i = {11, 20, 25, 32, 36, 40}, all at i = 16.

Is this a bug in the most recent release?  (If so, better let Wolfram know!)
Also, is there a way around it besides avoiding the use of sixteen?  It just
so happens that CForm[N[x, 16]] is absolutely ideal for sending data to a C
program with double precision reals...

     Jonathan
     johnsonj at mathcs.carleton.edu

     Mathematica user Mike Tie, mtie at mathcs.carleton.edu


----- End Included Message -----

I tried your problem on both a Unix kernel (Sun 386i) and a
MacIIx. Both version 1.2.1.  No bug for i={11,20} and I assume
the rest of the cases you tried.  What machine and what version
of Mathematica are you using?

Peace/Bob


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