What are the sources used for introducing hooks?

Hooks got the ideas from several different sources. Below are some of them,

1. Previous experiments with functional APIs in the react-future repository
2. Community experiments with render prop APIs such as Reactions Component
3. State variables and state cells in DisplayScript.
4. Subscriptions in Rx.
5. Reducer components in ReasonReact.

Practical Code Example

// Sources inspiring Hooks:
// Prior research in Functional Reactive Programming, algebraic effects, and ReasonML component state.