Question

I am curious about the following code, somebody could explain why does it call bool func first ? isn`t “str” more suitable for arg type string ?

 void a(bool input)
    {
        cout<<"I amd first"<<endl;
        cout<<input<<endl;
    }

    void a(const string &input)
    {
        cout<<"I amd second"<<endl;
        cout<<input<<endl;
    }

    int main( )
    {
        a("str");  //  call  void a(bool input)

        a(string("str"));   //call  void a(const string &input)

        return 0; 
    }

Answer 1

"str" is of type const char[4], which decays immediately to const char *, and the conversion from any pointer type to bool is considered before non-explicit constructors to custom types.

So, I’d say that the answer is "because the standard says so".

The relevant passage should be 13.3.3.2 ¶2:

When comparing the basic forms of implicit conversion sequences (as defined in 13.3.3.1)

• a standard conversion sequence (13.3.3.1.1) is a better conversion sequence than a user-defined conversion sequence or an ellipsis conversion sequence […]