What is the difference between template call?

Question

What is the difference between A, B and C calls?

#include <iostream>

using namespace std;

template<class T> T max(T a, T b) {
    return (a >= b) ? a : b;
}

int main() {
    float a = 4.0;
    float b = 6.0f;
    cout << max(a, b) << endl; //A
    cout << max<double>(a, b) << endl; //B
    cout << max<double>(4.0, 6.0f) << endl; //C
}

Answer 1

First invocation of max is actually max<float> , second and third is the same max<double>

But in second invocation both a and b get promoted to double, where in third the example only 6.0f is promoted to double.

Answer 2

A calls std::max<float> , since a and b are float arguments. In B and C, you force it to call std::max<double> , thus both arguments are converted to double.