Pointers are also useful for microoptimization of stepping through
arrays... but it wouldn't help JS without a lot of work in the engines...
for( var x = 0; x < width*height; x++ ) {
arr[x] = 3;
}
-----
var ptr = arr;
for( var x = 0; x < width*height; x++ ) {
ptr[0] = 3;
ptr++;
}
since a pointer plus a constant is always more efficient than a pointer
plus a variable amount that usually also has to be multiplied.
The second also serializes into SSE instructions when optimized so it can
do multiple loop steps at a time.
On Mon, Mar 19, 2018 at 3:20 PM, Isiah Meadows <[email protected]>
wrote:
> And even if we *could* get pointers into JS, I'd *strongly* not want
> it to be like what's proposed here. Instead, I'd prefer an object
> encapsulating a reference to a variable, something like this (although
> engines could avoid the ceremony of closures here):
>
> ```js
> let foo = 1;
>
> func(ref foo, bar)
> // Equivalent to:
> func({deref: () => foo, set: v => foo = v}, bar)
>
> function func(ref foo, bar) {
> foo += 2
> }
>
> // Equivalent to:
> function func(foo) {
> foo.set(foo.deref() + 2)
> }
> ```
>
> I've found myself more than once wanting a way to manipulate a
> variable by reference, in a way that's a bit more ergonomic than just
> creating a single-property object. It doesn't need to be much, but it
> doesn't need to be much. As a concrete example, recursive string
> joining could just pass a shared reference instead of an object with a
> single property:
>
> ```js
> function recursiveJoinLoop(ref str, array, sep) {
> if (Array.isArray(array)) {
> for (const item of array) recursiveJoinLoop(ref str, item, sep)
> } else {
> if (str == null) str = ""
> str += String(array)
> }
> }
>
> function recursiveJoin(array, sep) {
> let str
> for (const item of array) recursiveJoinLoop(ref str, array, sep)
> return str
> }
> ```
> -----
>
> Isiah Meadows
> [email protected]
>
> Looking for web consulting? Or a new website?
> Send me an email and we can get started.
> www.isiahmeadows.com
>
>
> On Mon, Mar 19, 2018 at 5:48 PM, Michael J. Ryan <[email protected]>
> wrote:
> > Please no, mutable objects are bad enough imho.
> >
> > On Mon, Mar 19, 2018, 12:47 Sebastian Malton <[email protected]>
> wrote:
> >>
> >> Proposal:
> >> Add a new variable-esk type called pointer which acts sort of like a
> >> reference to the data which it has been assigned to but modifies also
> the
> >> original reference when modified.
> >>
> >> Justification:
> >> When working with objects in particular it is often useful for satiny
> >> reasons to use local variables (mostly const's) as a shorthand reference
> >> both for compactness and also so that you don't have to type out the
> entire
> >> path every type. This would allow for non - objects but also overwriting
> >> objects if wanted but still have this freedom and convenience.
> >>
> >> Method:
> >> Add a new notation
> >>
> >> ```
> >> let:prt name = obj.field.name.fullname;
> >> ```
> >>
> >> Here if `name` is updated or if `obj.field.name.fullname` is updated so
> is
> >> the other.
> >>
> >> Sebastian Malton
> >>
> >> _______________________________________________
> >> es-discuss mailing list
> >> [email protected]
> >> https://mail.mozilla.org/listinfo/es-discuss
> >
> >
> > _______________________________________________
> > es-discuss mailing list
> > [email protected]
> > https://mail.mozilla.org/listinfo/es-discuss
> >
> _______________________________________________
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