iphone - how to find the permutations and combinations of any integer value? -

i want permutations , combinations in objective c.i have found both problem in code don't understand occurring. want print value in textfield prints last value entered. used code given below. me please..

    typedef enum{power,exponent,ncr,npr} calcoperation;     nsstring *storage;     calcoperation operation;    -(ibaction)combination{      operation = npr;      storage = label.text;     textfield.text=@"";     label.text = @"";     }     -(int) factorial:(int)n{    int d = n;    int temp = 1;    for(int b = 2; b <= d; b++){     temp = temp*b;    }   //nslog(@"the factorials = %i",temp);    return temp;  }   -(ibaction)equalbutton{   float tempo = [storage floatvalue];   float b = [label.text floatvalue];   nsstring *val = [[nsstring alloc]initwithformat:@"%f" , b];        switch(operation) {      case ncr:       textfield.text = [[nsstring alloc]initwithformat:@"%f",[self factorial:tempo] / ([self factorial:[val floatvalue]] * [self factorial:tempo-[val floatvalue]])];              //textfield.text = [[nsstring alloc]initwithformat:@"%f",[val floatvalue]+tempo+10];           nslog(@"combination %d",[self factorial:tempo] / ([self factorial:[val floatvalue]] * [self factorial:tempo-[val floatvalue]]));             break;     case npr:              textfield.text = [[nsstring alloc]initwithformat:@"%f",[self factorial:tempo] / [self factorial:tempo-[val floatvalue]]];             nslog(@"permutations %d",[self factorial:tempo] / ([self factorial:tempo-[val floatvalue]]));             break;  `                   }                 } 

//to calculate ncr n = tempo, r = b

int tempo = [storage intvalue]; int b = [label.text intvalue];  float tempcb =  (float)[self factorial:tempo] / ([self factorial:b] * [self factorial:tempo-b])];               break;