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POHow can i make a templated constructor allowing all of l-value ref, r-value ref and initializer_list?
 

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  1. POHow can i make a templated constructor allowing all of l-value ref, r-value ref and initializer_list?
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    <p>I'm trying to design a class which has two vectors of large sequences.</p> <pre><code>std::vector&lt;double&gt; factory() { return std::vector&lt;double&gt;{1,2,3}; // it actually generates a large sequence of double } struct my_class { my_class(const std::vector&lt;double&gt;&amp; x, const std::vector&lt;double&gt;&amp; y) : m_x(x), m_y(y) { } std::vector&lt;double&gt; m_x; std::vector&lt;double&gt; m_y; }; int main() { my_class c(factory(), factory()); my_class c2(factory(), {0.5, 1, 1.5}); } </code></pre> <p>Well, it works well but it doesn't use the move constructor of vector. So i tried to change the constructor to accept r-value references with perfect forwarding.</p> <pre><code>struct my_class { template&lt;typename X, typename Y&gt; my_class(X&amp;&amp; x, Y&amp;&amp; y , typename std::enable_if&lt;std::is_convertible&lt;X, std::vector&lt;double&gt; &gt;::value &amp;&amp; std::is_convertible&lt;Y, std::vector&lt;double&gt; &gt;::value&gt;::type * = 0 ) : m_x(std::forward&lt;X&gt;(x)), m_y(std::forward&lt;Y&gt;(y)) { } std::vector&lt;double&gt; m_x; std::vector&lt;double&gt; m_y; }; </code></pre> <p>And now i got a problem. When i try to construct an instance with an initializer_list, i got an error like this.</p> <pre><code>$ g++ -W -Wall -std=gnu++0x a.cpp a.cpp: In function ‘int main()’: a.cpp:34:32: error: no matching function for call to ‘my_class::my_class(std::vector&lt;double&gt;, &lt;brace-enclosed initializer list&gt;)’ a.cpp:17:18: note: candidate is: my_class::my_class(const my_class&amp;) </code></pre> <p>I thought that <code>std::initializer_list&lt;double&gt;</code> might not be convertible to <code>std::vector&lt;double&gt;</code>, but it actually is convertible and i got the same error when i tried without the enable_if argument. Am I missing something?</p>
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    1. USkukyakya
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      1. POHow can i make a templated constructor allowing all of l-value ref, r-value ref and initializer_list?
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    1. COOut of curiosity which version of g++ are you using? IIRC the `initializer_list` support was incomplete in several recent versions.
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    2. CO@awoodland I'm using gcc 4.6.2. What do you mean for 'imcomplete'?
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      1. USkukyakya
 

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