iphone - Finding and returning the distance between two coordinates -

i'm sort of newbie--please don't hate.

the method compiles, i'm not sure how retrieve float value (i.e. distance between 2 points) method returns (or should return rather).

-(float)finddistancebetween:(coordinate *)a and:(coordinate *)b { //distance formula:  //sqrt( (x2 - x1)^2 + (y2 - y1)^2 )  float resultdistance;   resultdistance = sqrt( pow((b.latitude - a.latitude), 2) + pow((b.longitude - a.longitude), 2));  return resultdistance;   }  //somewhere else...  float thedistancebetween;   //below incorrect:  thedistancebetween = [finddistancebetween: location1 and: location2];  

thanks

is finddistancebetween:and: defined in @implementation block? code should like

   // in .h file     @interface myclass : nsobject     // declaration of method    - (float)finddistanceinbetween:(coordinate *)a and:(coordinate *)b;    @end     // in .m file     @implementation myclass     // definition of method    - (float)finddistancebetween:(coordinate *)a and:(coordinate *)b {        return sqrt(powf(a.x - b.x, 2.f) + powf(a.y - b.y, 2.f));    }    @end     // somewhere else needs calculate difference:    // (assume coord_a , coord_b exist)     // create instance of myclass    myclass *myinstance = [[myclass alloc] init];     // send `finddistancebetween:and:` message instance    float distance = [myinstance finddistancebetween:coord_a and:coord_b];     // when you're done instance, need clean    [myinstance release]; 

it may make more sense put these types of methods on coordinate class can like:

   coordinate *coord_a = <get coordinate somewhere>;    coordinate *coord_b = <get coordinate somewhere>;     float distance = [coord_a distancefrom:coord_b];    float angle = [coord_a angleto:coord_b]; 

don't worry hating, new @ once. :)