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From Martin Sebor <se...@roguewave.com>
Subject Re: error on tuple copy ctor
Date Thu, 03 Jul 2008 03:17:50 GMT
Eric Lemings wrote:
>  
> 
>> -----Original Message-----
>> From: Martin Sebor [mailto:msebor@gmail.com] On Behalf Of Martin Sebor
>> Sent: Wednesday, July 02, 2008 3:18 PM
>> To: dev@stdcxx.apache.org
>> Subject: Re: error on tuple copy ctor
>>
> ...
>>> Should we add the ctor even if the standard does not 
>> (currently) specify it?
>>
>> I don't think it's needed or desirable. In the test case I
>> posted, we want to call the const T& overload.
> 
> That's the only workaround I can think of.  You have another one in
> mind?

Okay, now that we understand the rules and why a tuple lvalue
binds to the (variadic) template ctor instead of either the copy
or move ctor, I can't help but go back to one of first questions
I asked: if the non-const copy ctor is necessary, why doesn't
the spec mention it? Normally, when the spec leaves something
like this out it's either to allow different implementation
techniques, or it's an omission. In the first case, the
semantics tend to be described in terms of valid expressions.
In the second case it's up to us to fix it. I wonder which of
the two it is... Let me see if someone on c++std-lib can shed
some light on this.

Martin

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