Re: C++11 - Parameter pack question

Sidney Marshall <sidneym@xxxxxxxxxxxxxxx> · Sat, 16 Aug 2014 22:27:29 -0400

At 09:12 AM 8/16/2014 +0200, Marc Glisse wrote:
On Fri, 15 Aug 2014, Sidney Marshall wrote:

The following code compiles and runs correctly but gives a warning:

----------------------------------------
#include<iostream>

using namespace std;

template<class T>
T sum(T value) {
 return value;
}

template<class T, class ... U>
auto sum(T value, U ... values) {
   return value + sum(values ...);
}

int main() {
 cout << sum(1, 2, 4.6) << endl;
 cout << sum(1, "abcde", 2) << endl;
}
--------------------------------------

$ g++ -std=c++11 pack.cpp
pack.cpp:11:31: warning: â??sumâ?? function 
uses â??autoâ?? type specifier without trailing 
return type [enabled by default]
auto sum(T value, U ... values) {

The warning should probably specify that this is 
a C++14 feature. You should be compiling with -std=c++1y.

You are correct - I didn't read section 7.1.6.4 
paragraphs 2 and 5 of the standard correctly. Thank you.

I guess I can't write this function in C++11 this way.

--
Marc Glisse

--Sidney Marshall