This is the core issue for hooks as a concept

Hooks tell the outside after something has happened. They offer the ability to reject transitions, modify the internal data state, consume from the input tape, push onto the output tape, throw errors, halt the machine, or cause transitions. All of these things can be initiated from outside code.

Cross reference

Hook lifecycle is defined in #487. Notation is found in Hook notation #622, and short notation in #619. Transactionality is in #452. Required hooks are described in #620. Fluency is discussed in #596. Hook closure is in #617. The external hooking API is described in #700; the basic hooking API is described in #660, and the fluent in #699. Posthooks are covered in #896. Hook next is described in #952.

Specific hooks needed

The Basic hooks are almost done. The future hooks are mostly not.

todo: get the terminate variants and add them here

todo: hooks for data change