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Re: How many digits does octave use?!


From: John Eaton
Subject: Re: How many digits does octave use?!
Date: Tue, 12 Sep 1995 15:00:54 -0500

Ted Harding <address@hidden> wrote:

: Well, looking into this I typed the wrong thing, and ...
: 
: octave:28> sprintf("%.300g\n",1000000000/(8*8*8*8*8*8*8*8*8*8*8**88))
: ans = 3.1418198177905449939812940511912164115041379279996477216713...

If anything, this is a bug in the iostream library distributed with
libg++.  Octave uses the following method of printing numbers (except
that the format string is determined at run-time):

  #include <math.h>
  #include <iostream.h>
  int
  main (void)
  {
    cout.form ("%.70g\n", M_PI);
    return 0;
  }

When compiled with g++ and linked with libg++, this program prints

  3.141592653589793115997963468544185161590576171875

on my DEC Alpha.

I don't think it's worth working around this problem in Octave.  It
should be fixed in libg++ instead.

jwe


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