Mod operator in ios

问题:

have been searching for a mod operator in ios, just like the % in c, but no luck in finding it. Tried the answer in this link but it gives the same error. I have a float variable 'rotationAngle' whose angle keeps incrementing or decrementing based on the users finger movement. Some thing like this:

if (startPoint.x < pt.x) {
    if (pt.y<936/2) 
        rotationAngle += pt.x - startPoint.x;
    else
        rotationAngle += startPoint.x - pt.x;   
    }
    rotationAngle = (rotationAngle % 360);
}

I just need to make sure that the rotationAngle doesnot cross the +/- 360 limit. Any help any body. Thanks

回答1:

You can use fmod (for double) and fmodf (for float) of math.h:

#import <math.h>

rotationAngle = fmodf(rotationAngle, 360.0f);

回答2:

Use the fmod function, which does a floation-point modulo, for definition see here: http://www.cplusplus.com/reference/clibrary/cmath/fmod/. Examples of how it works (with the return values):

fmodf(100, 360); // 100
fmodf(300, 360); // 300
fmodf(500, 360); // 140
fmodf(1600, 360); // 160
fmodf(-100, 360); // -100
fmodf(-300, 360); // -300
fmodf(-500, 360); // -140

fmodf takes "float" as arguments, fmod takes "double" and fmodl takes "double long", but they all do the same thing.

回答3:

I cast it to an int first

rotationAngle = (((int)rotationAngle) % 360);

if you want more accuracy use

float t = rotationAngle-((int)rotationAngle);
rotationAngle = (((int)rotationAngle) % 360);
rotationAngle+=t;