Ctor to generate all possible combinations of array indices for a length r
array. This is a special-case optimization and is faster than simply
using the other ctor to generate all length r combinations from
seq(0, length).
For efficiency, uint is used instead of size_t since, on a 64-bit system,
generating all possible combinations of an array bigger than uint.max
wouldn't be feasible anyhow.
Ctor to generate all possible combinations of array indices for a length r array. This is a special-case optimization and is faster than simply using the other ctor to generate all length r combinations from seq(0, length).
For efficiency, uint is used instead of size_t since, on a 64-bit system, generating all possible combinations of an array bigger than uint.max wouldn't be feasible anyhow.