C++ template for loop which use loop counter as template argument

template_use_loop_counter_as_tpl_arg.cpp

#include <iostream>
#include <array>
 
template<size_t c>
struct ForLoop {
    template<template <size_t> class Func>
    static void iterate() {
        Func<c>()();
        ForLoop<c-1>::template iterate<Func>();
    }
};
 
template<>
struct ForLoop<0> {
    template<template <size_t> class Func>
    static void iterate() {
        Func<0>()();
    }
};

template <size_t size>
struct Foo {
    void operator()() {
        std::array<int, size> arr;
        std::cout << "Array size: " << arr.size() << std::endl;
    }
};

int main() {
    ForLoop<4>::iterate<Foo>();
}

Useful materials:

• http://stackoverflow.com/questions/10871100/pass-a-function-as-an-explicit-template-parameter

  The problem here is, multiply is not a type; it is a value but the function template bar expects the template argument to be a type. 
  

  So the Foo can't be just template function - instead it must be a struct.

• http://stackoverflow.com/questions/610245/where-and-why-do-i-have-to-put-the-template-and-typename-keywords

  X<c-1>::template forEach<Func>();
  

  The template is required here, because it is a dependent template