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Re: [v3 PATCH] Implement N4387 and LWG 2367


On Sun, 7 Jun 2015, Ville Voutilainen wrote:

On 7 June 2015 at 11:12, Ville Voutilainen <ville.voutilainen@gmail.com> wrote:
Does the following code still compile with your patch?
struct A { int a,b; };
std::tuple<int,int,A> a(3,4,{1,2});

No. :/ And we have no test for it.. I'll need to look at that.

Ahem, yes, this is because the constructor that used to take _Elements
now takes _UElements. I can change it back to take _Elements, because
the technique that the default constructors use allow making the signature
dependent enough that it will sfinae correctly.

Yes.

You use a lot: typename enable_if<X, bool>::type=true
while the current code seems to favor: class=typename enable_if<X>::type.
I don't really care which one is used, but it is easier to read when the
style is consistent through the library.
It's not a style issue. That template parameter needs to be a non-type one,
otherwise the overloads are ambiguous.

Ah, I had overlooked that. I have seen several work-arounds for this issue, but I don't remember this one, it seems nice.

--
Marc Glisse


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