[MATH-567] class Dfp toDouble method return -inf whan Dfp value is 0 "zero"

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.2
• Fix Version/s: 3.0
• Assignee: Unassigned
• Reporter: michel
• Created: 05/May/11 17:49
• Updated: 24/Mar/12 16:16
• Resolved: 05/May/11 19:44

Description

I found a bug in the toDouble() method of the Dfp class.
If the Dfp's value is 0 "zero", the toDouble() method returns a negative infini.

This is because the double value returned has an exposant equal to 0xFFF
and a significand is equal to 0.
In the IEEE754 this is a -inf.

To be equal to zero, the exposant and the significand must be equal to zero.

A simple test case is :
----------------------------------------------
import org.apache.commons.math.dfp.DfpField;

public class test {

/**

• @param args
  */
  public static void main(String[] args) { DfpField field = new DfpField(100); System.out.println("toDouble value of getZero() ="+field.getZero().toDouble()+ "\ntoDouble value of newDfp(0.0) ="+ field.newDfp(0.0).toDouble()); }

  }

May be the simplest way to fix it is to test the zero equality at the begin of the toDouble() method, to be able to return the correctly signed zero ?