rafa/src/core/EmptyEnumerator.js

Rafa.js is a Javascript framework for building concurrent applications.

// # constructor(): EmptyEnumerator
// An Enumerator that calls the callback with a DoneMessage when next is called 
// for the first time.
function EmptyEnumerator() {
  this.complete = false;
}

inherit(EmptyEnumerator, Enumerator, {

  // # next(callback: A => _)
  // Call a callback, passing a DoneMessage, on the first call to this method.
  // Subsequent calls throw CompleteError.
  next(callback) {
    if (this.complete) throw this.CompleteError;
    this.complete = true;
    callback(this.doneMessage());
  }
});