Re: [futures] Add convenience functions for immediate/canceled promises

It would also be nice to have something like Future.fails(x) because it is also occasionally useful to return a promise that immediately fails with a specific error.



________________________________
 From: Tab Atkins Jr. <jackalmage@gmail.com>
To: www-dom@w3.org 
Sent: Thursday, April 11, 2013 6:43 PM
Subject: [futures] Add convenience functions for immediate/canceled promises
 

Task.js has two convenience functions, now(x) and never(), which
return a resolved or cancelled promise, respectively.  This is useful
when combining plain values with the promise algebra, so the
combinators don't need to ducktype their arguments to try and guess
whether they're a promise or a plain value.  (Plus, it lets you easily
create a promise which resolves to a promise and use it in the
combinators.)

Separately, there's been discussion over at the PromisesAPlus github
about more explicitly supporting the fact that promises are monadic,
by defining a point/pure/return function that just returns a "default"
(fulfilled) promise from a base value
<https://github.com/promises-aplus/resolvers-spec/issues/24>.

Supporting these use-cases seem useful and simple.  We should add
Future.of(val) and Future.never() convenience static functions to the
Future interface.

~TJ