It's much used on meta-programming to provide optimizations.
It's better to avoid nesting what's already difficult.
Coping with complexity isn't necessarily the best solution.
Sorry if I disappoint you.
As an example of what I'm say, find below a quick example that will help optimize natural numbers exponentiation. It's slightly more elaborated than the one provided on C++ Templates: The Complete Guide by Nicolai Josuttis and Daveed Vandevoorde.
The first part is the "nested" meta-program:
template< unsigned long long B, unsigned char P >
struct exponentiation
{
enum
{
result = B * exponentiation< B, P - 1 >::result
};
};
template< unsigned long long B >
struct exponentiation< B, 0 >
{
enum
{
result = 1ULL
};
};
struct exponentiation
{
enum
{
result = B * exponentiation< B, P - 1 >::result
};
};
template< unsigned long long B >
struct exponentiation< B, 0 >
{
enum
{
result = 1ULL
};
};
The second part is (perhaps) a convenience wrapping:
template< unsigned long long B >
struct base
{
template< unsigned char P >
struct power
{
enum { result = exponentiation< B, P >::result };
};
};
The usage should be obvious:
char buffer[ base<2>::power<56>::result ];
The maximum compile-time capacity of Oracle Solaris Studio 12.3 for Solaris 11.1 running on Intel x64 is for computing the power of 2 to 61:
2305843009213693952
