使用类模板时的一点困惑

#include<string>
#include<iostream>

using namespace std;

///通过嵌套实现元则
template<typename T,typename N>
class my_tuple
{
public:
    T value;
    N next;
    my_tuple(T const &v,N const &n):value(v),next(n){}
};
template<typename T,typename N>
my_tuple<T,N> push(T const &v,N const &n)
{
    return my_tuple<T,N>(v,n);
}
int main()
{
    typedef my_tuple<int ,char> tuple2;
    typedef my_tuple<float,tuple2> tuple3;
    typedef my_tuple<std::string,tuple3> tuple4;

    tuple4 tup4 = push(std::string("awesome"),
27　　　　　　　　　　　　　　　push(.5f,push(2,'a')));
    cout<<tup4.value<<","
          <<tup4.next.value<",";
    cout<<tup4.next.next.value<<","
          <<tup4.next.next.next<<endl;
     //此时输出结果为: awesome,0.52,a
     //奇怪的是逗号少输出了一个
     //开始我用的输出格式是cout<<tup4.value<<","<<tup4.next.value<","<<tup4.next.next.value<<","<<tup4.next.next.next<<endl;
     //直接就报错了：test.cpp||error: invalid operands of types 'const char [2]' and 'int' to binary 'operator<<'
}

希望大神们看到了能给出一点提示