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

On 27/03/2012, Zeke <xanadu860122(a)gmail.com&gt; wrote: > Whether the comparison is precarious or not should depend on how you handle > the literal. If you handle 99.9 as BigDecimal("99.9") which precision can > be controlled, you can trust the comparison. > Wait a sec: primarily, you are testing a double, and this is where some unavoidable imprecision is introduced. These are some doubles close to 99.9: a 99.899999999999990000 0x1.8f99999999999p6 b 99.900000000000000000 0x1.8f9999999999ap6 c 99.900000000000020000 0x1.8f9999999999bp6 a < 99.9 is the true value truncated, b > 99.9 is rounded (the next binary digit being 1). There just isn't a double == 99.9. (Don't be confused by b's printed value.) The BigDecimal value 99.90000000000001 you have observed is due to rounding the result of new BigDecimal( (double)99.9 ), i.e. 99.900000000000005684341886080801486968994140625 It's easy to see that a better value is obtained by using a String value: new BigDecimal( "99.9" ) but I don't know whether your Drools version would let you write doubleValue == "99.9". If you want/have to stick with 4.x you might use public static final doubles defined in some Java class instead of the magic 99.9. This should avoid the sidestep into BigDecimal and the ensuing conversion confusion. -W _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users