Node style lifting function for promises

node-style-lift.coffee

# Promises

{ Deferred } = require 'promise.coffee'
fs = require 'fs'

emptyPromise = ->
  def = new Deferred
  def.resolve(undefined)
  return def.promise

nodeStyleLift = (nodefn) ->
  ->
    def = new Deferred
    args = [].slice.call arguments
    args.push (err, res) ->
        if err? then def.reject(err) else def.resolve(res)
    ->
      nodefn.apply this, args
      return def.promise

readFileAsync = nodeStyleLift fs.readFile

emptyPromise()
.then readFileAsync("package.json", "utf8")
.then (value) ->
  console.log value