乘以0时NaN错误JAVA

Question

I really can't understand why this expression gives me a NaN error only when

acceleration.module - Ambient.friction = 0

:

double x = (speed.module * speed.direction.x()) + ((acceleration.module-Ambient.friction) * acceleration.direction.x())*time;

Moreover if I add pharentesis like these:

double x = ((speed.module * speed.direction.x()) + ((acceleration.module-Ambient.friction) * acceleration.direction.x()))*time;

it gives me a NaN error again.

Answer 1

In the first, the second value is multipled by time.

double x = (speed.module * speed.direction.x()) + ((acceleration.module-Ambient.friction) * acceleration.direction.x())*time;

For the other, the whole thing is multiplied by time:

double x = ((speed.module * speed.direction.x()) + ((acceleration.module-Ambient.friction) * acceleration.direction.x()))*time;

This makes me think you are overflowing the double values in the second one before you multiple with time. With double overflow you get the magic values Double.POSITIVE_INFINITY or Double.NEGATIVE_INFINITY

Most likely you are multiplting time with Double.POSITIVE_INFINITY or Double.NEGATIVE_INFINITY and the result is NAN.

Change the calculations to a series of steps. With each step, check the result for overflow, by looking for Double.POSITIVE_INFINITY or Double.NEGATIVE_INFINITY. That will tell you where things go off the rails. You are almost certainly overflowing somewhere, but we cannot see the numbers you are handling so I cannot tell you exactly where.

Answer 2

我（受过教育的）猜测是nan已经在这个方向上，因为当模块为零时它将不确定