remainder function

[Ether]

Originally Posted by Radical Pi

drem() does exist, and is defined to be the same as remainder() (see the glibc manual).

Apparently in glibc, remainder() and drem() are two different names for the same function

Notice the very slight difference between the glibc and Java definitions (handling of divide-by-zero).

[nightpool]

The "java" link you posted was to gnu libc...

[Ether]

Originally Posted by nightpool

The "java" link you posted was to gnu libc...

Fixed. Take a look.

[Ether]

Originally Posted by Joe Ross

Here's the result from the robot

        double result;
        double x[] = {179, 180, 181, 359, 721, -1, -179, -180, -359, -361, -721};

        for (int i = 0; i < x.length; i++){
            result = MathUtils.IEEEremainder(x[i],360.0); 
            System.out.println("x: " + x[i] + " rem y: 360 result: " + result);
        }

Joe, is the MathUtils.IEEEremainder() method available in 2015 FRC Java, now that the runtime engine has changed? If so, does it produce the exact same results?

[Joe Ross]

Originally Posted by Ether

Joe, is the MathUtils.IEEEremainder() method available in 2015 FRC Java, now that the runtime engine has changed? If so, does it produce the exact same results?

It's in Math, rather then the squawk MathUtils workaround, but it still works.

x: 179.0 rem y: 360 result: 179.0
x: 180.0 rem y: 360 result: 180.0
x: 181.0 rem y: 360 result: -179.0
x: 359.0 rem y: 360 result: -1.0
x: 721.0 rem y: 360 result: 1.0
x: -1.0 rem y: 360 result: -1.0
x: -179.0 rem y: 360 result: -179.0
x: -180.0 rem y: 360 result: -180.0
x: -359.0 rem y: 360 result: 1.0
x: -361.0 rem y: 360 result: -1.0
x: -721.0 rem y: 360 result: -1.0

[Ether]

Originally Posted by Joe Ross

It's in Math, rather then the squawk MathUtils workaround, but it still works.

Thanks Joe.

For those of you reading this thread for the first time, Math.IEEEremainder(angle,360.0) can be used to convert any angle (in degrees) to the range -180 to 180.

This can be very useful when working with the gyro.

Let's say you want to find the shortest angular error between your joystick direction angle and the gyro angle. This can be accomplished in one clean line of code as follows:

angle_error = Math.IEEEremainder(joystick-gyro,360.0);

There's no need for conditional logic. It cleanly handles all input angle ranges for joystick and gyro, including angles greater than 360 degrees and less than -360 degrees.

The above assumes that gyro and joystick share the same zero and measurement direction.