std::basic_string<CharT,Traits,Allocator>::basic_string

#include <iostream>
#include <cassert>
#include <iterator>
#include <string>
#include <cctype>

int main()
{
  {
    // string::string()
    std::string s;
    assert(s.empty() && (s.length() == 0) && (s.size() == 0));
  }

  {
    // string::string(size_type count, charT ch)
    std::string s(4, '=');
    std::cout << s << '\n'; // "===="
  }

  {
    std::string const other("Exemplary");
    // string::string(string const& other, size_type pos, size_type count)
    std::string s(other, 0, other.length()-1);
    std::cout << s << '\n'; // "Exemplar"
  }

  {
    // string::string(charT const* s, size_type count)
    std::string s("C-style string", 7);
    std::cout << s << '\n'; // "C-style"
  }

  {
    // string::string(charT const* s)
    std::string s("C-style\0string");
    std::cout << s << '\n'; // "C-style"
  }

  {
    char mutable_c_str[] = "another C-style string";
    // string::string(InputIt first, InputIt last)
    std::string s(std::begin(mutable_c_str)+8, std::end(mutable_c_str)-1);
    std::cout << s << '\n'; // "C-style string"
  }

  {
    std::string const other("Exemplar");
    std::string s(other);
    std::cout << s << '\n'; // "Exemplar"
  }

  {
    // string::string(string&& str)
    std::string s(std::string("C++ by ") + std::string("example"));
    std::cout << s << '\n'; // "C++ by example"
  }

  {
    // string(std::initializer_list<charT> ilist)
    std::string s({ 'C', '-', 's', 't', 'y', 'l', 'e' });
    std::cout << s << '\n'; // "C-style"
  }

  {
    // overload resolution selects string(InputIt first, InputIt last) [with InputIt = int]
    // which behaves as if string(size_type count, charT ch) is called
    std::string s(3, std::toupper('a'));
    std::cout << s << '\n'; // "AAA"
  }
}