What does template <unsigned int N> mean?
c++, non-type-template-parameter, templates
Solution
It's perfectly possible to template a class on an integer rather than a type. We can assign the templated value to a variable, or otherwise manipulate it in a way we might with any other integer literal:
unsigned int x = N;
In fact, we can create algorithms which evaluate at compile time (from Wikipedia):
template <int N>
struct Factorial
{
enum { value = N * Factorial<N - 1>::value };
};
template <>
struct Factorial<0>
{
enum { value = 1 };
};
// Factorial<4>::value == 24
// Factorial<0>::value == 1
void foo()
{
int x = Factorial<4>::value; // == 24
int y = Factorial<0>::value; // == 1
}
Problem
When declaring a template, I am used to having this kind of code: ``` template <class T> ``` But in this question, they used: ``` template <unsigned int N> ``` I checked that it compiles. But what does it mean? Is it a non-type parameter? And if so, how can we have a template without any type parameter?