bounded

bounded<bound> is a type representing a dynamic value with a compile-time upper bound.

It is intended for use cases where it is important to know statically the largest value a variable can take.

For example, bounded<16> could bound a for loop:

// the value of n may not be greater than 16
bounded<16> n = 10;

#pragma unroll
for(int i = 0; i != n.bound; ++i)
{
  if(i < n)
  {
    f(i);
  }
}

One might write a loop this way to encourage unrolling and predication in an effort to minimize warp divergence in CUDA code.

Arithmetic between bounded and constant can track upper bounds in some cases:

bounded<10> a = 7;
bounded<50> b = 42;

// the sum of a + b may be no larger than 60
auto c = a + b; // the type of c is bounded<60>

bounded<20> d = 13;
auto e = 42_c;

// the product of c * d may be no larger than 840
auto f = d * e; // the type of f is bounded<840>