// static_assert works at compile time 
// It's the only way to check if template parameters make sense!
#include <iostream>
#include <vector>
#include <array>
#include <string>
#include <type_traits>


template <typename T>
void func(std::vector<T> & vec)
{
  static_assert(std::is_integral<T>::value||std::is_floating_point<T>::value,"func: Vector type must be int or float");
  std::cout<<"ok, got number data; func call ok\n";
  // Operation that follow make sense only for numerical values
}

int main()
{
  std::vector<double> v1(10);
  std::vector<int> v2(10);
  std::vector<std::string> v3(10);
  func(v1); // ok
  func(v2); // ok
  func(v3); // won't compile, static assertion in func fails
  
  // type traits:
  std::cout<<"std::is_floating_point<int>::value    = "<<std::is_floating_point<int>::value<<"\n";
  std::cout<<"std::is_integral<int>::value          = "<<std::is_integral<int>::value<<"\n";
  std::cout<<"std::is_floating_point<double>::value = "<<std::is_floating_point<double>::value<<"\n";

}