Question

#include <iostream>
using namespace std;

template <typename x> x functionA (x, x);

int main ()
{
    functionA <double, double, double> (1, 1) << "\n";
}

template <typename x> x functionA (x arg1, x arg2)
{
    return arg1 + arg2;
}

This code results in:

error: no matching function for call to ‘functionA(int, int)’

What can be the reasons?

Answer 1

The function template has one template parameter only, and you’re passing 3 template arguments to it:

functionA <double, double, double> (1, 1) << "\n";

Why 3 template arguments?

Just write:

functionA <double> (1, 1);

Or you can simply let the compiler deduce the template argument, as:

functionA(1.0, 1.0);  //template argument deduced as double!
functionA(1, 1);     //template argument deduced as int!