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Newsgroups: comp.lang.java.programmer
Subject: Re: higher precision doubles
Date: Sat, 06 Aug 2011 13:29:41 -0700
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On 8/6/2011 12:24 PM, Jan Burse wrote:
> Motivating example, in Go we have:
...
> In Java we have:
...
> zero1=-2.4492935982947064E-16
> zero2=-2.4492935982947064E-16


I honestly don't find this very motivating. Zero is what you make of it. 
  In engineering I learning that 6 digits are sufficient for almost any 
practical task.  30 is way overkill.

As far as printing is concerned, don't get confused by the funny 
numbers.  It's just a matter of understanding and selecting the correct 
format.

Counter motivating example:

public class FpPrint {

     public static void main( String[] args )
     {
         System.out.printf( "%6.6f\n", Math.sin( Math.PI * 2 ) );
         System.out.printf( "%6.6f\n", StrictMath.sin( StrictMath.PI * 2 
) );
     }
}

run:
-0.000000
-0.000000
BUILD SUCCESSFUL (total time: 0 seconds)


Here we understand what significant digits mean, and we print the 
correct and desired number of digits.  We're good.

There's many times many accumulated errors between 0 and 2 x 10^-16 . 
Just because the default Java printer doesn't print a "0" doesn't mean 
we should panic.  That's really all your demonstrating here: the default 
printing behavior of System.out.println.