C++11中auto关键字的编译错误

Question

I know that the use of auto keyword can automatically deduce the type of the variable from the Rvalue. Then why does the following function snippet in my code have a compilation error?

auto getName(auto str = "John Doe") {
    return str;
}

The compilation error is 'auto' not allowed in function prototype. I googled a bit and I think auto can not be used in the function prototypes. Why So?

Answer 1

You can use auto in a lambda expression, but not a normal function.

To get the same effect, you can define a function template instead:

template <class T>
T getname(T input = "John Doe") {
    return input;
}

But be aware that this default value for the argument will only work for types that can actually be initialized from a string literal.

Oh, and as an aside, names starting with str are reserved, so it would be better to use a different name.