Definition:Basic Primitive Recursive Function/Identity Function

Definition

The identity function $I_\N: \N \to \N$ is a basic primitive recursive function, defined as:

$\forall n \in \N: \map {I_\N} n = n$

Note that this is an implementation of the projection function:

$\pr_1^1: \N \to \N: \map {\pr_1^1} {n_1} = n_1$

It is URM computable by a single-instruction URM program.