Chief Delphi - Crio Square Roots

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tekman1001

15-02-2009 10:15

Crio Square Roots

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

15-02-2009 10:18

Re: Crio Square Roots

Quote:

Originally Posted by tekman1001 (Post 821202)

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

15-02-2009 10:23

Re: Crio Square Roots

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

15-02-2009 11:18

Re: Crio Square Roots

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

15-02-2009 11:32

Re: Crio Square Roots

Second sentinel, make sure you #include <cmath>

bronxbomber92

15-02-2009 12:40

Re: Crio Square Roots

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:

Code:

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;

}

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