monads.future

A monad for time-dependant values, providing explicit effects for delayed computations, latency, etc.

monads.future

The Future(a, b) monad represents values that depend on time. This allows one to model time-based effects explicitly, such that one can have full knowledge of when they're dealing with delayed computations, latency, or anything that can not be computed immediately.

A common use for this monad is to replace the usual [Continuation-Passing Style][CPS] form of programming, in order to be able to compose and sequence time-dependent effects using the generic and powerful monadic operations.

var Future = require('monads.future')
 
function get(url) {
  return new Future(function(resolvereject) {
    var request = new XMLHttpRequest()
    request.onload = function() {
      if (!/2\d\d/.test(this.status))  reject(this.responseText)
      else                             resolve(this.responseText)
    }
    request.open("get", url, true)
    request.send()
  })
}
 
var t1 = get('/something')
var t2 = get('/other')
 
var t3 = t1.map(function(a) {
           t2.map(function(b) {
             return a + b
           })
         })
 
t3.chain(function(a) {
  console.log(a)
})

The easiest way is to grab it from NPM. If you're running in a Browser environment, you can use [Browserify][]

$ npm install monads.future

If you're not using NPM, [Download the latest release][release], and require the monads.future.umd.js file:

var Future = require('monads.future')

[Download the latest release][release], and require the monads.future.umd.js file:

require(['monads.future'], function(Future) {
  ( ... )
})

[Download the latest release][release], and load the monads.future.umd.js file. The properties are exposed in the global Future object:

<script src="/path/to/monads.future.umd.js"></script>

If you want to compile this library from the source, you'll need [Git][], [Make][], [Node.js][], and run the following commands:

$ git clone git://github.com/folktale/monads.future.git
$ cd monads.future
$ npm install
$ make bundle

This will generate the dist/monads.future.umd.js file, which you can load in any JavaScript environment.

You can [read the documentation online][docs] or build it yourself:

$ git clone git://github.com/folktale/monads.maybe.git
$ cd monads.maybe
$ npm install
$ make documentation

Then open the file docs/literate/index.html in your browser.

This library assumes an ES5 environment, but can be easily supported in ES3 platforms by the use of shims. Just include [es5-shim][] :)

Copyright (c) 2013 Quildreen Motta.

Released under the MIT licence.

[Fantasy Land]: https://github.com/fantasyland/fantasy-land [Browserify]: http://browserify.org/ [release]: https://github.com/folktale/monads.future/releases/download/v0.2.0/monads.future-0.2.0.tar.gz [Git]: http://git-scm.com/ [Make]: http://www.gnu.org/software/make/ [Node.js]: http://nodejs.org/ [es5-shim]: https://github.com/kriskowal/es5-shim [docs]: http://folktale.github.io/monads.future [CPS]: http://matt.might.net/articles/by-example-continuation-passing-style/