C++: What are template parameters and how do they work?

1// Function template
2template<typename T>
3T max(T a, T b) {
4    return (a > b) ? a : b;
5}
6
7int result = max(3, 5);       // Compiler generates max<int>
8double d = max(2.5, 3.5);    // Compiler generates max<double>
9
10// Class template
11template<typename T, size_t N>
12class Array {
13    T data[N];
14public:
15    T& operator[](size_t i) { return data[i]; }
16    constexpr size_t size() const { return N; }
17};
18
19Array<int, 10> arr;
20arr[0] = 42;