As a sidenote, but with regard to forEach, can someone point me to some
documentation that explains why the generic form of forEach doesn't work with
objects (the use case has sufficient history)
Rick
-- Sent from my Palm Pre
On Jul 10, 2011 6:42 PM, David Bruant <david.bru...@labri.fr> wrote:
Le 10/07/2011 22:46, Dmitry A. Soshnikov a écrit :
Here I put some extensions for arrays standard library (separated
from this thread:
https://mail.mozilla.org/pipermail/es-discuss/2011-July/015856.html
where Array.of and Array.from were considered).
We can consider also the following (as a first step):
- Array.prototype.remove(value, all)
[1, 2, 3, 2].remove(2); // [1, 3, 2]
[1, 2, 3, 2].remove(2, true); // [1, 3]
(seems this function is required more than Array.of, because at
least I saw it implemented in all frameworks and used it myself).
- Array.prototype.subtract(array)
[1, 2, 3, 4].subtract([2, 4]); // [1, 3]
- Array.seq(from, to) // or Array.range(from, to)
Array.seq(1, 5); // [1, 2, 3, 4, 5]
- Array.build(n, fn)
Array.build(5, function(index) index + 1); // [1, 2, 3, 4, 5]
- Array.min(array), Array.max(array) (can be implemented
with Math.max/min and apply though)
Array.min = (array) -> Math.min.apply(Math, array)
- Array.prototype.split(n)
["a", "b", "c", "d", "e"].split(3) // [["a", "b", "c"], ["d", "e",
"f"]]
Perhaps even to build objects from lists of keys and values (this
function is usually called as `zip`):
- Object.fromArrays(["a", "b", "c"], [1, 2, 3]); // {a: 1,
b: 2, c: 3}
- Array.prototype.unique
[1, 3, 2, 5, 5, 3].unique(); // [1, 3, 2, 5]
Thus, all names of methods can be discussed.
I like a lot all of these ideas, but I can't help thinking that they
do not seem to be aligned with the initial ECMAScript array design
which is that arrays are ECMAScript objects (which is very different
from what we'd understand of "array" in C or "lists" in Erlang as
you cite them).
The question I ask for each of your Array.prototype ideas is "how
does it apply to non-dense arrays?".
Creating a List or a DenseArray (or both?) type sounds to better
capture your intentions (especially since you provided a link to
Erlang "list" methods). It could inherit everything from
Array.prototype for free.
Actually, this could be implemented with proxies :-)
Since we're suggesting array additions, I would be interested in
trying to address one issue of forEach, map, every, some and filter.
They all have a well-defined algorithm. Consequently, if the
callback function has side-effects, these are deterministic. This,
however, prevent efficient (parallelized, for instance)
implementation. This is unfortunate since in a lot of cases, people
don't do side-effect and would certainly trade the side-effect
determinism guarantee for performance.
Could it be considered to add non-deterministic versions of these
functions? They would be defined like Array.prototype.sort is, in
terms of guarantees (like "the callback function will be called at
most once on which array element" for 'every' and 'some' for
instance) rather than with an algorithm.
I have no strong opinion on how to name them. Maybe adding an N (for
"Non-deterministic") at the end of the equivalent method
(Array.prototype.forEachN, Array.prototype.mapN, etc.)?
David
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