Standard library header <bitset>

#include <string>
#include <iosfwd>   // 用于 istream, ostream
namespace std {
  template<size_t N> class bitset;
  // bitset 运算符
  template<size_t N>
    constexpr bitset<N> operator&(const bitset<N>&, const bitset<N>&) noexcept;
  template<size_t N>
    constexpr bitset<N> operator|(const bitset<N>&, const bitset<N>&) noexcept;
  template<size_t N>
    constexpr bitset<N> operator^(const bitset<N>&, const bitset<N>&) noexcept;
  template<class CharT, class Traits, size_t N>
    basic_istream<CharT, Traits>&
      operator>>(basic_istream<CharT, Traits>& is, bitset<N>& x);
  template<class CharT, class Traits, size_t N>
    basic_ostream<CharT, Traits>&
      operator<<(basic_ostream<CharT, Traits>& os, const bitset<N>& x);
}

namespace std {
  template<size_t N> class bitset {
  public:
    // 位引用
    class reference {
    public:
      constexpr reference(const reference&) = default;
      constexpr ~reference();
      constexpr reference& operator=(bool x) noexcept;           // 用于 b[i] = x;
      constexpr reference& operator=(const reference&) noexcept; // 用于 b[i] = b[j];
      constexpr bool operator~() const noexcept;                 // 翻转位
      constexpr operator bool() const noexcept;                  // 用于 x = b[i];
      constexpr reference& flip() noexcept;                      // 用于 b[i].flip();
    };
    // 构造函数
    constexpr bitset() noexcept;
    constexpr bitset(unsigned long long val) noexcept;
    template<class CharT, class Traits, class Allocator>
      constexpr explicit bitset(
        const basic_string<CharT, Traits, Allocator>& str,
        typename basic_string<CharT, Traits, Allocator>::size_type pos = 0,
        typename basic_string<CharT, Traits, Allocator>::size_type n
          = basic_string<CharT, Traits, Allocator>::npos,
        CharT zero = CharT('0'),
        CharT one = CharT('1'));
    template<class CharT, class Traits>
      constexpr explicit bitset(
        basic_string_view<CharT, Traits> str,
        typename basic_string_view<CharT, Traits>::size_type pos = 0,
        typename basic_string_view<CharT, Traits>::size_type n
          = basic_string_view<CharT, Traits>::npos,
        CharT zero = CharT('0'),
        CharT one = CharT('1'));
    template<class CharT>
      constexpr explicit bitset(
        const CharT* str,
        typename basic_string_view<CharT>::size_type n = basic_string_view<CharT>::npos,
        CharT zero = CharT('0'),
        CharT one = CharT('1'));
    // 位集操作
    constexpr bitset& operator&=(const bitset& rhs) noexcept;
    constexpr bitset& operator|=(const bitset& rhs) noexcept;
    constexpr bitset& operator^=(const bitset& rhs) noexcept;
    constexpr bitset& operator<<=(size_t pos) noexcept;
    constexpr bitset& operator>>=(size_t pos) noexcept;
    constexpr bitset  operator<<(size_t pos) const noexcept;
    constexpr bitset  operator>>(size_t pos) const noexcept;
    constexpr bitset& set() noexcept;
    constexpr bitset& set(size_t pos, bool val = true);
    constexpr bitset& reset() noexcept;
    constexpr bitset& reset(size_t pos);
    constexpr bitset  operator~() const noexcept;
    constexpr bitset& flip() noexcept;
    constexpr bitset& flip(size_t pos);
    // 元素访问
    constexpr bool operator[](size_t pos) const;
    constexpr reference operator[](size_t pos);
    constexpr unsigned long to_ulong() const;
    constexpr unsigned long long to_ullong() const;
    template<class CharT = char,
             class Traits = char_traits<CharT>,
             class Allocator = allocator<CharT>>
      constexpr basic_string<CharT, Traits, Allocator>
        to_string(CharT zero = CharT('0'), CharT one = CharT('1')) const;