On Jul 10, 2011, at 3:51 PM, Rick Waldron wrote: > 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)
You mean: why wasn't Array.prototype.forEach put on Object in the first place? The array extras loop from 0 up to but not including this.length -- they're not enumerating properties. Enumeration of Array elements is unspecified and browsers behave differently (as for enumeration of indexed properties in non-Arrays, and of properties in general). Non-interoperation and no normative spec to appeal to, combined with the focus on Array not Object, kept forEach simple, and congruent to the other [0, this.length) indexing generics. /be > > Rick > > > > -- Sent from my Palm Pre > > On Jul 10, 2011 6:42 PM, David Bruant <[email protected]> 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 > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss
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