Crio Square Roots

[tekman1001]

Hi our crio is giving us errors when we try to do square roots using sqrt(variable)
Where variable is obviously a variable. any help would be usefully and appreciated.

[EricVanWyk]

Originally Posted by tekman1001

Hi our crio is giving us errors when we try to do square roots using sqrt(variable)
Where variable is obviously a variable. any help would be usefully and appreciated.

We're going to need a bit more info to help you out here.

What errors are you getting? What does your code look like?

[tekman1001]

When we try to download to the crio it tells us it cannot find the function. The code looks like this "Kvar = Dvar / sqrt(PrecentVar);"

[Sentient]

It may be that WPILib doesn't have a sqrt function. I honestly don't know what WPILib has implemented, but sqrt() is usually in "math.h", which is a Windows Library (or whatever OS you are using).

[tdlrali]

Second sentinel, make sure you #include <cmath>

[bronxbomber92]

If for some reason you're having problems beyond #included <cmath> (in which case, you should probably fix anyways :-P) here's a nice implementation of sqrt for floats taken from quake:

float SquareRootFloat(float number) {
    long i;
    float x, y;
    const float f = 1.5F;

    x = number * 0.5F;
    y  = number;
    i  = * ( long * ) &y;
    i  = 0x5f3759df - ( i >> 1 );
    y  = * ( float * ) &i;
    y  = y * ( f - ( x * y * y ) );
    y  = y * ( f - ( x * y * y ) );
    return number * y;
}