Quadrille.singleton

Declares that one value is meant to be shared by every cell — the whole quadrille holds the same instance, not one copy per cell. The call changes nothing: it returns the value untouched, and exists to say so where a reader will look.

fill(value) already stores the very same reference in every cell it fills, so Quadrille.singleton(v) is a statement of intent rather than a transformation. That intent matters once the value is an object with state: a shared instance means a change made through one cell is visible through all of them, which is what a wall, a counter or a rule object usually wants.

Example

Note

The opposite is Quadrille.factory: a function run per cell, so every cell receives its own value. A quadrille filled with a singleton is one object seen many times; a quadrille filled with a factory is many objects.