rafa/src/core/DoneMessage.js

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

// # constructor(value: A): DoneMessage
// The last message sent though a stream that didn"t error out  and contains 
// the last value.
function DoneMessage(value) {
  this.value = value;
  if (value === undefined) {
    this.isValue = false;
    this.map = this.contextid;
  }
}

inherit(DoneMessage, Message, { 
  isDone: true,

  // # filter(predicate: A => Bool): DoneMessage
  // Unlike the normal filter on a message, the done message must never return
  // `undefined` since it should still continue walking the tree, so if the
  // predicate does not match, return a new done message without a value.
  filter(predicate) {
    return predicate(this.value) ? this : new DoneMessage();
  }
});