Re: [rules-users] [rules user] different behavior on double type

4.0.7 is rather old. 5.1.1 and later do not exhibit this behaviour. However, it should be noted that comparing double values using == is a precarious approach. For instance, 99.9 (the mathematical number) cannot be represented as a double machine number. Hence, you do not truly test for equality with that number, just with its approximation by some machine number. -W On 26/03/2012, Zeke <xanadu860122(a)gmail.com&gt; wrote: > Hi, guys: > I am using Drools 4.0.7. I find a strange behavior. When my LHS is > "Message( varDouble == 99.9 )" and "varDouble" equals "new Double(99.9)", > the condition is true. But when my LHS is "Message( types.doubleType == > 99.9 )" and the "doubleType" field is also equal to "new Double(99.9)", the > condition is false. I debug the code, and find that: > > When the LHS is "Message( varDouble == 99.9 )", the logic will handle the > literal 99.9 as *Double.valueOf( “99.9” )*, and the comparison is between > *(new > Double(99.9)).doubleValue(*) and *Double.valueOf( “99.9” ).doubleValue()*, > When the LHS is "Message( types.doubleType == 99.9 )", the logic is > different from above. The comparison is between *new BigDecimal((Double) > 99.9, MathContext.DECIMAL64)* (which double value is 99.90000000000001) and > *new BigDecimal(“99.9”, MathContext.DECIMAL64)* (which double value is > 99.9). > > I think we need make things consistent. "varDouble" and > "types.doubleType" are of the same type and value. It doesn't make sense to > have different behavior just because of one field is nesting while the > other is not. I know Drools is using MVEL to evaluate the condition. But I > am not sure it is a MVEL bug or Drools uses MVEL wrong. It will be much > appreciated if you can give me any comments! > _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users