24 Strings library [strings]

24.2 Character traits [char.traits]

24.2.3 char_­traits specializations [char.traits.specializations]

24.2.3.4 struct char_­traits<wchar_­t> [char.traits.specializations.wchar.t]

namespace std {
  template<> struct char_traits<wchar_t> {
    using char_type  = wchar_t;
    using int_type   = wint_t;
    using off_type   = streamoff;
    using pos_type   = wstreampos;
    using state_type = mbstate_t;

    static constexpr void assign(char_type& c1, const char_type& c2) noexcept;
    static constexpr bool eq(char_type c1, char_type c2) noexcept;
    static constexpr bool lt(char_type c1, char_type c2) noexcept;

    static constexpr int compare(const char_type* s1, const char_type* s2, size_t n);
    static constexpr size_t length(const char_type* s);
    static constexpr const char_type* find(const char_type* s, size_t n,
                                           const char_type& a);
    static char_type* move(char_type* s1, const char_type* s2, size_t n);
    static char_type* copy(char_type* s1, const char_type* s2, size_t n);
    static char_type* assign(char_type* s, size_t n, char_type a);

    static constexpr int_type not_eof(int_type c) noexcept;
    static constexpr char_type to_char_type(int_type c) noexcept;
    static constexpr int_type to_int_type(char_type c) noexcept;
    static constexpr bool eq_int_type(int_type c1, int_type c2) noexcept;
    static constexpr int_type eof() noexcept;
  };
}
1
#
The defined types for int_­type, pos_­type, and state_­type shall be wint_­t, wstreampos, and mbstate_­t respectively.
2
#
The type wstreampos shall be an implementation-defined type that satisfies the requirements for pos_­type in [iostreams.limits.pos] and [iostream.forward].
3
#
The type mbstate_­t is defined in <cwchar> and can represent any of the conversion states that can occur in an implementation-defined set of supported multibyte character encoding rules.
4
#
The two-argument members assign, eq, and lt shall be defined identically to the built-in operators =, ==, and < respectively.
5
#
The member eof() shall return WEOF.