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Subject: Re: [boost] C++03 unique_ptr emulation
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2009-01-08 14:17:52

Howard Hinnant wrote:
> On Jan 8, 2009, at 12:42 PM, Ion Gaztañaga wrote:
>> is quite problematic for container implementation. With the old
>> emulation (that returned detail::rv<T>) this was possible:
>> class vector
>> {
>> void push_back(const value_type &);
>> void push_back(boost::detail::rv<value_type>);
>> }
> Is it practical to do this instead?
> class vector
> {
> void push_back(value_type x); // internally move construct from x
> }

I see that adobe vector has two overloads that are activated with
enable_if-like expressions:

template <typename U>
void push_back(const U& x, typename copy_sink<U, T>::type =

template <typename U>
void push_back(U x, typename move_sink<U, T>::type = 0);

Not that I totally dislike the solution but forwarding is a problem that
has a more difficult solution since we can't avoid the overhead for
non-movable types. For example:

template<class T1, class T2, class T3,...
iterator emplace_back(???, ???, ???, ...)?

v.emplace_back(t1, boost::move(t2), t3, ...)

The same happens when implementing forwarding functions, so I'm starting
to think that putting T() in functions taking movable-only types by
value is not a bad idea ;-)



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