On Fri, 16 Aug 2019 at 17:52, Brian Bi via Std-Discussion
<std-discussion@lists.isocpp.org> wrote:
> Which pack expansion in this example does not use an ellipsis?
> There are two pack expansions here: `...xs=args` where the pattern is `xs=args`,
That's not a pack expansion. It's a declaration of a captured pack,
initialized from another pack. It does not
and should not use a trailing ellipsis.
> and also in `bar(xs...)`, `xs...` is a pack expansion. Both use an ellipsis.
That one is fine, yes.
> The `sizeof...` operator also contains an ellipsis. It just happens that the ellipsis is not adjacent to the pack.
It contains an ellipsis but it's not a pack expansion.
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That's not what the plain text of the standard says (C++17 [temp.variadic]/4):
Pack expansions can occur in the following contexts: ... In a capture-list (8.1.5); the pattern is a capture. In a sizeof... expression (8.3.3); the pattern is an identifier.
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