Definition:Basic Primitive Recursive Function/Projection Function

Definition
The projection functions $\operatorname{pr}^k_j: \N^k \to \N$ are basic primitive recursive functions, defined as:
 * $\forall \left({n_1, n_2, \ldots, n_k}\right) \in \N^k: \operatorname{pr}^k_j \left({\left({n_1, n_2, \ldots, n_k}\right)}\right) = n_j$

where $j \in \left[{1 \,.\,.\, k}\right]$.

They are each URM computable by a single-instruction URM program.