replaceAll function in C++

replaceAll.cpp

#include <iostream>
using std::cout;
using std::endl;

#include <string>
using std::string;
using std::basic_string;

#include <string_view>
using std::basic_string_view;

template <typename CharT>
basic_string<CharT>& replaceAll(basic_string<CharT>& str, basic_string_view<CharT> old_str, basic_string_view<CharT> new_str) {
  typename basic_string_view<CharT>::size_type old_len(old_str.size());
  typename basic_string_view<CharT>::size_type new_len(new_str.size());
  typename basic_string<CharT>::size_type pos(0);

  while ((pos = str.find(old_str, pos)) != basic_string<CharT>::npos) {
    str.replace(pos, old_len, new_str);
    pos += new_len;
  }

  return str;
}

int main(void) {
  string a{"你好，世界！世界！！"};
  cout << replaceAll<char>(a, "世界", "地球人") << endl;

  return 0;
}