C++ 'typedef' vs. 'using ... = ...'
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?
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.
链接地址: http://www.djcxy.com/p/78646.html上一篇: 在C ++中使用奇怪的声明