Meiosis pattern in typescript (a simple example)

Meiosis.ts

// uses 'flyd' stream micro-library

type Stream = (_: number) => Stream // this life is a simplification

interface Model {
	value: number
}

interface Actions {
	increment: () => void
	decrement: () => void
}


interface App {
	Initial: () => Model
	Actions: (_: Stream) => Actions
}

// ==============

const app: App = {
	Initial = () => { value: 0 }
	Actions = _stream => {
		increment: () => _stream(1),
		decrement: () => _stream(-1),
	}
}

const update = flyd.stream() // #1 - update stream
const states = flyd.scan(    // #3 - scan update stream with initial value
	(state, increment) => // and apply patchs to the state with an reducer funcion
		state.value = state.value + increment
, app.Initial(), update)

const actions = app.Actions(update) // #2 - Push actions on stream

states.map( state =>	// # 4 - map to display stream
	document.write("<pre>" + JSON.stringify(state) + "</pre>")
	   
//run
actions.increment()
actions.increment()
actions.decrement()

MeiosisGenericWithFunctionPatches.ts

// More generic version
// Using Function Patches

interface State {
  temperature: {
    value: number
    units: 'C'
  }
}

const initialState: State {
  temperature: {
    value: 22,
    units: 'C'
  }
}

//action
const increment = amount => update( state => state.temperature.value += amount )

//reducer
const update = flyd.stream()
const states = flyd.scan( (state, patch) => patch(state), initialState, update ) 

//
const actions = temperature.Actions(update)
state.map( state => document.write(
  '<pre> + JSON.stringfy(state, null, 2) + '</pre>'
))