Apologies again, I'm a beat or three behind today. I think you gave the
example already:
expr1.flatMap(x =>
expr2(x).flatMap(y => ...
exprN(x, y, ...).map(z =>
result(x, y, ..., z)
)
)
)
Nice when Scala and JS look alike!
I don't think we'd make comprehensions return a monad, specifically a
Promise, even if we had the silly things (Promises, I mean -- just
teasing about monads) in the language.
JS is eager and mutational. Although Mark and I have discussed privately
trying to get E-like "featureless" promises, which become their
fulfillment value, we think it's too big a stretch. Especially in light
of existing libraries, but even starting fresh.
Without E-like featureless/"becoming" promises, I wouldn't foist them on
syntax for eager computations such as comprehensions and generator
expressions.
So is the explicit functional style, with arrows for sugar, really too much?
/be
Brendan Eich wrote:
Brendan Eich wrote:
Mike Stay wrote:
On Fri, May 10, 2013 at 1:07 PM, Brendan Eich<[email protected]>
wrote:
What's wrong with the iteration protocol?
Nothing at all for arrays. For every other monad, there's no sugar:
the only monad multiplication that's supported is list concatenation.
Iteration is much more general than "arrays".
Oh, sorry -- you mean comprehensions (not the iteration protocol,
which is used by all for-of syntax) are only about creating fresh arrays.
Yes, that's true. One alternative is a generator expression, which
doesn't build any eager data structure, rather iterates and yields
values on demand.
As Jason pointed out, arrows sweeten the explicit monadic patterns,
e.g. monadic Promises. To close this thread it would be helpful to see
an example where you use all the ES6 sugar, and then say why you'd
still want another special form.
/be
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