comonadic futures on top of Q

task.coffee

Q = require './q'                                                                                                                                                                         
        
class exports.Task
  constructor: (@promise) ->
        
  value: null
  reason: null
        
  result: ->
    unless @promise.isResolved()           
      throw 'cannot ask for result of unresolved task'      
    if @reason?
      throw @reason
    @value
        
  continueWith: (cb) ->
        
    generateHandler = (fn) => (value) =>
      t0 = new Task @promise
      fn t0, value
      next = cb t0
      if next? then (Q.defer next).promise else null
        
    success = generateHandler (t0, value) -> t0.value = value
    failure = generateHandler (t0, reason) -> t0.reason = reason
        
    new Task @promise.then success, failure