c++ iterative combination function not working -

i have homework problem asking write iterative , recursive combination function. place them in given program see takes longer.

i having problem iterative function. have gone on several times , keep getting mach-o-linker error. have tried identifying variables many different ways , still haven't come luck.

any on topic appreciated. think there problem iterator function or possibly factorial function, unable see life of me right now.

thanks again ahead of time

#include <iostream> #include <sys/time.h> #include <cstdlib> using std::cout; using std::endl;  double ir; double in;  typedef unsigned int uint;  uint factorial(uint n)   {   if (n == 0) return 1;    if (n <= 2) return n;     else return n * factorial(n - 1);   }    double combination_recursive(double in, double ir);   double combination_iterative(int in, int ir);      int main(int argc, const char * argv[]) {   typedef struct timeval time; time stop, start; gettimeofday(&start, null);  in = 20.0; ir = 3.0;     combination_iterative(in, ir);   gettimeofday(&stop, null); if(stop.tv_sec > start.tv_sec)     cout << "seconds: " << stop.tv_sec-start.tv_sec << endl;   else     cout << "micro: " << stop.tv_usec-start.tv_usec << endl;   return 0; }  double comination_iterative(int, int) {    if (in == ir) { return 1;}    if (ir == 0 && in!= 0) { return 1;}   else return (in * factorial(in-1))/factorial(in-1)*factorial(in-ir);   }  double combination_recursive(double in, double ir) {   if (ir < 0 || ir > in) {       return 0; }   if (ir < 1) {     return 1; }   if (in == ir) {     return 1; } return combination_recursive(in - 1, ir) + combination_recursive(in - 1, ir - 1); } 

i think error due simple misspelling.

you make call function in main

combination_iterative(in, ir); 

but have defined as

double comination_iterative(int, int) {  if (in == ir) { return 1;}  if (ir == 0 && in!= 0) { return 1;}   else return (in * factorial(in-1))/factorial(in-1)*factorial(in-ir); } 

to fix change function definition match call

double combination_iterative(int, int) {  if (in == ir) { return 1;}  if (ir == 0 && in!= 0) { return 1;}   else return (in * factorial(in-1))/factorial(in-1)*factorial(in-ir); } 

happy coding , learning c++