Note that unlike most programs which maintain a linear undo history, Vim maintains an undo tree containing every edit made to a buffer.

The Trash Can is a temporary holding area for accounts, properties, and views before they are deleted. Accounts, properties, and views are moved to the Trash Can and held for 35 days before they are permanently deleted.

Patches form the basis of any proper undo / redo system. (Snapshots don’t support undo / redo well in multi actor systems; they tend to undo everybody’s changes when going back in time.

A mathematical function does not execute any code — it just knows the answer. A Haskell function has to calculate the answer.

you can’t have a set of all sets