16 Library introduction [library]

enum enumerated { ${\text{V}}_0$, ${\text{V}}_1$, ${\text{V}}_2$, ${\text{V}}_3$, … };

inline const ${\text{enumerated C}}_0$(${\text{V}}_0$);
inline const ${\text{enumerated C}}_1$(${\text{V}}_1$);
inline const ${\text{enumerated C}}_2$(${\text{V}}_2$);
inline const ${\text{enumerated C}}_3$(${\text{V}}_3$);
  ⋮

// For exposition only.
// int_­type is an integral type capable of representing all values of the bitmask type.
enum bitmask : int_type {
  ${\text{V}}_0$ = 1 << 0, ${\text{V}}_1$ = 1 << 1, ${\text{V}}_2$ = 1 << 2, ${\text{V}}_3$ = 1 << 3, …
};

inline constexpr ${\text{bitmask C}}_0$(${\text{V}}_0$);
inline constexpr ${\text{bitmask C}}_1$(${\text{V}}_1$);
inline constexpr ${\text{bitmask C}}_2$(${\text{V}}_2$);
inline constexpr ${\text{bitmask C}}_3$(${\text{V}}_3$);
  ⋮

constexpr bitmask operator&(bitmask X, bitmask Y) {
  return static_cast<bitmask>(
    static_cast<int_type>(X) & static_cast<int_type>(Y));
}
constexpr bitmask operator|(bitmask X, bitmask Y) {
  return static_cast<bitmask>(
    static_cast<int_type>(X) | static_cast<int_type>(Y));
}
constexpr bitmask operator^(bitmask X, bitmask Y){
  return static_cast<bitmask>(
    static_cast<int_type>(X) ^ static_cast<int_type>(Y));
}
constexpr bitmask operator~(bitmask X){
  return static_cast<bitmask>(~static_cast<int_type>(X));
}
bitmask& operator&=(bitmask& X, bitmask Y){
  X = X & Y; return X;
}
bitmask& operator|=(bitmask& X, bitmask Y) {
  X = X | Y; return X;
}
bitmask& operator^=(bitmask& X, bitmask Y) {
  X = X ^ Y; return X;
}

• (4.1)
  To set a value Y in an object X is to evaluate the expression X |= Y.
• (4.2)
  To clear a value Y in an object X is to evaluate the expression X &= ~Y.
• (4.3)
  The value Y is set in the object X if the expression X & Y is nonzero.

• (1.1)
  A letter is any of the 26 lowercase or 26 uppercase letters in the basic execution character set.
• (1.2)
  The decimal-point character is the (single-byte) character used by functions that convert between a (single-byte) character sequence and a value of one of the floating-point types. It is used in the character sequence to denote the beginning of a fractional part. It is represented in [support] through [thread] and [depr] by a period, '.', which is also its value in the "C" locale, but may change during program execution by a call to setlocale(int, const char*),158 or by a change to a locale object, as described in [locales] and [input.output].
• (1.3)
  A character sequence is an array object A that can be declared as T A[N], where T is any of the types char, unsigned char, or signed char ([basic.fundamental]), optionally qualified by any combination of const or volatile. The initial elements of the array have defined contents up to and including an element determined by some predicate. A character sequence can be designated by a pointer value S that points to its first element.