[expr.unary.op] Notes naming unary ops as {ones',two's} complement

The terms "one's complement" and "two's complement" are well-known,
and it is useful to associate them with these operators.

Author: tkoeppe

source/expressions.tex

@@ -4653,6 +4653,10 @@
 of an unsigned quantity is computed by subtracting its value from $2^n$,
 where $n$ is the number of bits in the promoted operand. The type of the
 result is the type of the promoted operand.
+\begin{note}
+The result is the two's complement of the operand
+(where operand and result are considered as unsigned).
+\end{note}
 
 \pnum
 \indextext{operator!logical negation}%
@@ -4674,6 +4678,10 @@
 the coefficient $\tcode{r}_i$
 of the base-2 representation of the result \tcode{r}
 is 1 if $\tcode{x}_i$ is 0, and 0 otherwise.
+\begin{note}
+The result is the ones' complement of the operand
+(where operand and result are considered as unsigned).
+\end{note}
 There is an ambiguity
 in the grammar when \tcode{\~{}} is followed by
 a \grammarterm{type-name} or \grammarterm{decltype-specifier}.