Could someone explain from where that value get ?

Question

i wrote for fun calculate on template too work with double and int. i wrote somthing like that
code :
#include <iostream>
using namespace std;

template <class Cal1>
Cal1 sum(Cal1 a, Cal1 b) {
return a+b;
}
template <class Cal1>
Cal1 sub(Cal1 a, Cal1 b){
return a-b;
}
template <class Cal1>
Cal1 mul(Cal1 a, Cal1 b){
return a*b;
}
template <class Cal1>
Cal1 divi(Cal1 a, Cal1 b){

if (a != 0 && b != 0){

return a/b;
}
else {
cout << "Error division by 0 ";
}

}

int main() {
double x=0.0 , y=2.0;
cout << sum(x,y) << endl << sub(x,y) << endl;
cout << mul(x,y) << endl;
cout << divi(x,y);
return 0;
}
its working but i get some additional output and i don't know how too kick that
output:
2
-2
0
Error division by 0 1.#QNAN
what is that 1.#QNAN ?
thx for explains

Answer 1

ok i find where it's it :) function return result of a/b. I just add return 0 line.

Answer 2

right my mistake ;)

Answer 3

i write wrong condition: if ( a!=0 && b!=0)
now i edit it and its just if (b!=0)

Answer 4

its not division by 0. you are doing 0.0/2.0, which is 0.0

Answer 5

so from where did the division by zero output came from?