Definition:Pair Coding

Definition
Let $x, y \in \N$ be natural numbers.

Let $\pi : \N^2 \to \N$ be the Cantor pairing function.

Let $n = \map \pi {x, y}$.

Then $n \in \N$ codes the pair $\tuple {x, y}$, or $n$ is the code number for the pair $\tuple {x, y}$.