CWG2626 Rephrase ones' complement using base-2 representation

Author: burblebee

source/expressions.tex

@@ -4672,11 +4672,17 @@
 The type of the result is \keyword{bool}.
 
 \pnum
-\indextext{signed integer representation!ones' complement}%
 \indextext{operator!ones' complement}%
-The operand of \tcode{\~{}} shall have integral or unscoped enumeration type; the
-result is the ones' complement of its operand. Integral promotions are
-performed. The type of the result is the type of the promoted operand.
+The operand of \tcode{\~{}} shall have integral or unscoped enumeration type.
+Integral promotions are performed.
+The type of the result is the type of the promoted operand.
+% FIXME: [basic.fundamental]/p5 uses $x_i$; [expr] uses $\tcode{x}_i$.
+Given the coefficients $\tcode{x}_i$
+of the base-2 representation\iref{basic.fundamental}
+of the promoted operand \tcode{x},
+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.
 There is an ambiguity
 in the grammar when \tcode{\~{}} is followed by
 a \grammarterm{type-name} or \grammarterm{decltype-specifier}.