Goodbye "bit" in C++, (Partially)

C++2a(C++20)言語仕様の定義においては、用語 "bit" の利用はできるだけ回避される(完全に無くなる訳ではない)。これはC++2a言語仕様変更「符号付き整数型==2の補数表現を保証」の影響。

提案文書 P1236R1 Alternative Wording for P0907R4 Signed Integers are Two's Complement 冒頭部より引用。

This paper presents alternative wording for P0907R3 Signed Integers are Two's Complement by Jean François Bastien, avoiding talking about unobservable bits as much as possible.


整数型サイズの表現では、独自の用語 "range exponent" が利用される。N4800(C++2a WD) 6.7.1/p4より一部引用。

Table 10 -- Minimum range exponent

Type Minimum range exponent N
signed char 8
short 16
int 16
long 32
long long 64

The range exponent of each signed integer type shall not be less than the values specified in Table 10. The value representation of a signed or unsigned integer type comprises N bits, where N is the respective range exponent. Each set of values for any padding bits (6.7) in the object representation are alternative representations of the value specified by the value representation. (snip)