Promise.cast and Promise.resolve

Juan Ignacio Dopazo jdopazo at yahoo-inc.com
Tue Jan 28 10:20:00 PST 2014


On Tuesday, January 28, 2014 10:13 AM, Kevin Smith <zenparsing at gmail.com> wrote:


>My take is that the difference between "cast" and "resolve" is so
>subtle that I don't think it captures developer intention. In
>other words, if I see some code calling Promise.cast(otherPromise),
>I can't be sure that the developer made an intentional choice over
>Promise.resolve(otherPromise).
>

Note that `Promise.resolve(p)`, where p is a promise, does *not* return an eventual for the eventual value of p.  Rather, it returns an eventual for p, literally.  Promises should be considered fully parametric (in other words, nestable).

That's not true as per the last consensus. There was `Promise.fulfill(p)` which would've nested promises, but it was left for ES7 to investigate fulfill+flatMap.

Juan
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