Print and count ints

gistfile1.txt

#include <iostream>
#include <vector>
#include <algorithm>
#include <type_traits>
#include <functional>
#include <numeric>

// give the two templates
// need to write the variadic template
// need to explain what is going on.

/*
template<typename T>
std::ostream& operator<<(std::ostream& out, const std::vector<T>& v) {
  out << "[";
  if(v.begin() != v.end()) {
    out << *v.begin();
    std::for_each(v.begin()++, v.end(), [&out](const T& t){ out << " " << t; });
  }
  out << "]";
  return out;
}*/

template <typename T>
constexpr bool printIfWholeNumber(const T&,
    typename std::enable_if<!std::is_arithmetic<T>::value,
                         T>::type* =0) {
  // std::cout << "FAILED: " << t << std::endl;
  return false;
}

template <typename T>
constexpr bool printIfWholeNumber(const T& i,
    typename std::enable_if<std::is_arithmetic<T>::value, T>::type* =0) {
  if(std::trunc(i) == i) {
    std::cout << i;
    return true;
  }
  return false;
}

template <typename T>
constexpr unsigned int printAndCountWholeNumbers(const T& d) {
  if (printIfWholeNumber(d)) {
    std::cout << " ";
    return 1;
  }
  return 0;
}

template <typename T>
constexpr unsigned int printAndCountWholeNumbers(const std::vector<T>& vec) {
  return std::accumulate(vec.begin(), vec.end(), 0U, [](const unsigned int& t, const T& v){
      if(printAndCountWholeNumbers(v)) {
        return t+1;
      } else {
        return t;
      }
      });
}

// disclaimer: this is bad. We'll talk about perfect forwarding later
template <typename HEAD, typename... TAIL>
constexpr unsigned int printAndCountWholeNumbers(HEAD head, TAIL... tail) {
  return printAndCountWholeNumbers(head)+printAndCountWholeNumbers(tail...);
}

int main() {

  printIfWholeNumber(std::string("Hello world!"));
  printIfWholeNumber(2.0f);
  printIfWholeNumber(std::vector<double>());

  // why does 7.0 not get printed?
  auto c = printAndCountWholeNumbers(1,2.5,3,4.5,5.5,6,7.0,-5,"2");
  std::cout << "count = " << c << std::endl;

  // why does 32 print this time?
  std::vector<double> d = {1.2,32.0,3.2,5.30,5.4,6,-5};
  auto dc = printAndCountWholeNumbers(d);
  std::cout << "count = " << dc << std::endl;

  std::vector<unsigned int> vui = { 65,343,21,3};
  dc = printAndCountWholeNumbers(vui);
  std::cout << "count = " << dc << std::endl;
}

was thinking for about 10 mins and didnt crack why 7.0 not get printed... but it does
https://godbolt.org/z/7dGG768fE

Interesting... You're right, though I don't remember the context of this gist (at all) so I'm not sure that I actually believed the content of the comments.