Promise.cast and Promise.resolve

Sébastien Cevey seb.cevey at guardian.co.uk
Wed Jan 29 04:04:03 PST 2014


On 29 Jan 2014 03:42, "Brendan Eich" <brendan at mozilla.com> wrote:

> And so we will go with 'chain'.

I assume it has been pointed out before that Underscore/LoDash have
popularised their own "chain" function/concept?

http://underscorejs.org/#chaining

Hopefully it's distant enough from Promise-world to alleviate most
confusion, but I thought I'd point it out for completeness.


On the flatMap name, as a Scala developer, I find it quite conveniently
describes the "flattening" nature of the operation, although it only really
works thanks to the parallel with map:

M[A]#map(f: A => B): M[B]
M[A]#flatMap(f: A => M[B]): M[B]
(not M[M[B]] as it would with map - hence the "flat")

But given that 'then' is a sort of a mix of map/flatMap (and flatThen is
terrible), I don't think there is an obvious parallel currently.

Seeing as flatMap/chain is being discussed though, have there been plans to
add a map method on Promises (that would map to a new Promise without
unwrapping returned promises)?

And have there been any discussion to add other monadic types to ES, eg
Option/Maybe, Try, etc, or to make existing types support more monadic
operations, eg Array.prototype.flatMap (or "chain"?).

Thanks, and sorry if this has been discussed before (is there any way to
"catch up" on such topics if it has, short of reading piles of minutes?).


On 29 January 2014 03:42, Brendan Eich <brendan at mozilla.com> wrote:

> Quildreen Motta wrote:
>
>> I suppose using names that don't give you a hint of the meaning of the
>> operation fits perfectly Haskell's (and Scalaz's) "Avoid Success At All
>> Costs" tradition
>>
>
> lulz.
>
> And so we will go with 'chain'.
>
> /be
>
>
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>



-- 
Sébastien Cevey
Software Developer

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