Nontype parameters for templates

Besides the template arguments that are preceded by the class or typename keywords , which represent types, templates can also have regular typed parameters, similar to those found in functions. As an example, have a look at this class template that is used to contain sequences of elements

// sequence template
#include <iostream>
using namespace std;
template <class T, int N>
class mysequence {
T memblock [N];
public:
void setmember (int x, T value);
T getmember (int x);
};
template <class T, int N>
void mysequence<T,N>::setmember (int x, T value) {
memblock[x]=value;
}
template <class T, int N>
T mysequence<T,N>::getmember (int x) {
return memblock[x];
}
int main () {
mysequence <int,5> myints;
mysequence <double,5> myfloats;
myints.setmember (0,100);
myfloats.setmember (3,3.1416);
cout << myints.getmember(0) << '\n';
cout << myfloats.getmember(3) << '\n';
return 0;
}

It is also possible to set default values or types for class template parameters. For example, if the previous class template definition had been:


            
template <class T=char, int N=10> class mysequence {..};
            
            
We could create objects using the default template parameters by declaring:


            
mysequence<> myseq;
            
            
Which would be equivalent to:


            
mysequence<char,10> myseq;