C++ nan keeps coming up with integration

Question

I am trying to get a integration program running but I keep getting the nan when computing. i have no idea whats wrong with my code.

    #include <iostream>
    #include <cmath>
    using namespace std;


    int main(){
cout << "For integration up \n";
   for (int z=0; z<=5; z++){
   int i=1;
   float nathan [6] = {pow(10,2), pow(10,3), pow(10,4), pow(10,5),pow(10,6), pow(10,7)};
   int h= nathan[z];
   int n=0;
   double x= (h-i)/h;
   double y= (h-i)/h;
   double t= 0;


   while(n <= h){


     if(n == 0){
    t += (x/3)*(1/y);
  }else if(n==h){
     t+= (x/3)*(1/y);
  }else if(n%2 ==1){
        t+= (4*x/3)*(1/y);
        }else{t+= (2*x/3)*(1/y);
        }

y= x+y;
n = n+1;
   }

   cout << "The integration of 1/x for N = "<< nathan[z] <<" is equal to " << t << endl;

   }

   }

can someone please help me out with this...

Answer 1

it s because x and y are always 0 in your code because h is int. When you do (h-i)/h, the compiler assumes that (h-i) is int and h is also int so it also assumes that the result of the ratio is int. This ratio is between 0 and 1 so when you only represent it with an int, it is just 0. And only after that the compiler cast this value to a double, which then remains 0. Try with :

   double x= (h-i)/(double)h;
   double y= (h-i)/(double)h;