Why does 0.06 + 0.01 = 0.07 in ColdFusion?

问题

Why don't math operations in ColdFusion seem to be affected by floating point math issues? Take the code:

result = 0.06 + 0.01;

writedump(result);
writedump(result.getClass().getName());

Which outputs

0.07

java.lang.Double

However the equivlant Java code produces what I"d expect when adding two doubles:

public static void main(String[] args) {
    double a = 0.01d;
    double b = 0.06d;

    System.out.println(a + b); //0.06999999999999999
}

This is what I'd expect to see from ColdFusion because of the realities of floating math (http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html).

Does ColdFusion do some "magic" behind the scenes or am I looking at an isolated anomaly here?

回答1:

I strongly suspect it's simply rounding differently on output. In other words, the issue is still there - it just happens not to show up when this particular value is printed out with writedump.

What happens if you use:

writedump(String.valueOf(result));

?

来源：https://stackoverflow.com/questions/7422510/why-does-0-06-0-01-0-07-in-coldfusion