Pointwise Addition is Associative

Theorem
Let $S$ be a non-empty set.

Let $\mathbb F$ be one of the standard number sets: $\Z, \Q, \R$ or $\C$.

Let $f, g, h: S \to \mathbb F$ be functions.

Let $f + g: S \to \mathbb F$ denote the pointwise sum of $f$ and $g$.

Then:
 * $\left({f + g}\right) + h = f + \left({g + h}\right)$

That is, pointwise addition is associative.

Specific Contexts
This result can be applied and proved in the context of the various standard number sets: