naive prototype of coroutine

coroutine.js

function _go(g, step) {
  while(!step.done) {
    //run the closure function
    const [state, value] = step.value()

    switch (state) {
      case "park":
        // just wait, add to eventloop
        // setImmediate(function() { _go(g, step) })
        setTimeout(function() { _go(g, step) })
        return
        
      case "continue":
        // continue until park
        step = g.next(value)
        break
    }
  }
}

function go(gen) {
  const g = gen()
  // g.next is hof put or take
  _go(g, g.next())
}

function put(c, val) {
  return function() {
    if(c.length == 0) {
      // pre-append FILO
      c.unshift(val)
      return ["continue", null]
    }
    
    return ["park", null]
  }
}

function take(chan) {
  return function() {
    if(chan.length == 0) {
      return ["park", null]
    }
    // take until chan empty
    const val = chan.pop()
    return ["continue", val]
  }
}

// def the channel
const c = []

// recursively, put one and get one
go(function * () {
  for (let i = 0; i < 10; i++) {
    yield put(c, i)
    console.log('put: ', i)
  }

  yield put(c, null)
})

go(function * () {
  while (true) {
    const val = yield take(c)
    
    if(val == null) {
      console.log('nothing more')
      return
    }
    
    console.log('take: ', val)
  }
})