35 

    36 CGFloat CGPointDot(CGPoint a,CGPoint b) {

    37     return a.x*b.x+a.y*b.y;

    38 }

    39 

    40 CGFloat CGPointLen(CGPoint a) {

    41     return sqrtf(a.x*a.x+a.y*a.y);

    42 }

    43 

    44 CGPoint CGPointSub(CGPoint a,CGPoint b) {

    45     CGPoint c = {a.x-b.x,a.y-b.y};

    46     return c;

    47 }

    48 

    49 CGFloat CGPointDist(CGPoint a,CGPoint b) {

    50     CGPoint c = CGPointSub(a,b);

    51     return CGPointLen(c);

    52 }

    53 

    54 CGPoint CGPointNorm(CGPoint a) {

    55     CGFloat m = sqrtf(a.x*a.x+a.y*a.y);

    56     CGPoint c;

    57     c.x = a.x/m;

    58     c.y = a.y/m;

    59     return c;

    60 }