C++ 'typedef' vs. 'using ... = ...' [duplicate]

Question

Possible Duplicate:
What are the differences between typedef and using in C++11?

The following code compiles and runs. My question is what is the difference between the "typedef" and "using" method for renaming the template specialization?

template<typename T>
struct myTempl{
    T val;
};

int main (int, char const *[])
{
    using templ_i = myTempl<int>;
    templ_i i;
    i.val=4;

    typedef myTempl<float> templ_f;
    templ_f f;
    f.val=5.3;

    return 0;
}

Edit:

If there is no difference, which one would you prefer? / Why was the using ... = ... version introduced?

Vaseline

A using that is not a template is not really the use-case this was introduced for. – Partain

-1. exact dublicate: #10748310 – Entoderm

@Entoderm You're right, I just wan't able to find that. – Vaseline

@Simon: first link in google: google.com/… – Entoderm

Have you noticed that C++11 is moving to a left-to-right declaration style everywhere? The use of using to write type alias is more consistent with new C++11 style. The phrase is from Herb Sutter herbsutter.com/2013/08/12/… – Horny

Answer 1

They are the same.

To quote the C++11 standard (or the draft to be specific):

A typedef-name can also be introduced by an alias-declaration. The identifier following the using keyword becomes a typedef-name and the optional attribute-specifier-seq following the identifier appertains to that typedef-name. It has the same semantics as if it were introduced by the typedef specifier. In particular, it does not define a new type and it shall not appear in the type-id.

I think the "the same semantics as the typedef specifier" say it all.

Silurid