events = require 'events'
util = require './util'
factory = util.factory
Module that provides a series of expressions that re-evaluate automatically whenever one of the leaf nodes of the expression tree changes.
events = require 'events'
util = require './util'
factory = util.factory
The Value instances represent an active value that changes with
time. The actual value can be accessed via the value
property.
Whenever the value changes, a value
event is notified, using the
standard node.js events
system. To register a listener callback that is called whenever the
value changes, use the on
method from the events.EventEmitter
interface.
class exports.Value extends events.EventEmitter
constructor: ({initial}={}) ->
super
@setMaxListeners 0
if initial?
@value = initial
@property 'value',
get: -> @_value
set: (newValue) ->
@setValue newValue
setValue: (newValue) ->
if @_value != newValue
@_value = newValue
@emit 'value', newValue
@_value
exports.value = factory exports.Value
Constants are lightweight objects that behave like a exports.Value, but can not be modified — at least, they will not trigger a modification when modified.
class exports.Const
value: undefined
constructor: (initial=undefined) ->
@value = initial
It has to mock the events.EventEmitter interface.
on: ->
addListener: ->
removeListener: ->
listeners: -> []
exports.const = factory exports.Const
Higher order values take a function as a parameter and a set of other values.
A Reduce value combines N values applying a reduction (i.e. fold) operation on them. It updates whenever one of them changes.
class exports.Reduce extends exports.Value
constructor: (@reducer, @reduced...) ->
super()
for v in @reduced
v.on 'value', => @update()
@update()
update: ->
@value = @reduced
.reduce((a, b) => exports.const @reducer a.value, b.value)
.value
exports.reduce = factory exports.Reduce
exports.and = -> exports.reduce ((a, b) -> a and b), arguments...
exports.or = -> exports.reduce ((a, b) -> a or b), arguments...
A Transform value holds a transformation of some other value by a unary function.
class exports.Transform extends exports.Value
constructor: (@transformer, @transformed) ->
super()
@transformed.on 'value', => @update()
@update()
update: ->
@value = @transformer @transformed.value
exports.transform = factory exports.Transform
exports.not = -> exports.transform ((a) -> not a), arguments...
Copyright (C) 2013 Juan Pedro Bolívar Puente
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.