Lazy evaluation

Michał Wadas michalwadas at gmail.com
Fri Sep 1 07:16:55 UTC 2017


Stage 2, but they move really slow.

On 1 Sep 2017 9:15 am, "Andrea Giammarchi" <andrea.giammarchi at gmail.com>
wrote:

> I thought decorators were nowhere higher than stage 0 (since ever)
>
> On Thu, Aug 31, 2017 at 9:53 PM, Michał Wadas <michalwadas at gmail.com>
> wrote:
>
>> Why not something like decorators (not sure if decorator  proposal covers
>> this already)?
>>
>> class Foo {
>> @cached
>> get bar() {
>> return something(this);
>> }
>> }
>>
>> On 31 Aug 2017 10:30 pm, "Andrea Giammarchi" <andrea.giammarchi at gmail.com>
>> wrote:
>>
>> it's a matter of semantics.
>>
>> If I see this
>>
>> ```js
>> var later = anyWrappingName(() => Math.random());
>>
>> // this is an assumption, not something obvious
>> later() === later()
>> ```
>>
>> If instead, I write this:
>> ```js
>> this.later === this.later;
>> ```
>>
>> I expect that to never possibly fail like `arr.length === arr.length` or
>> any `obj.prop`, in APIs with common sense, are equal to `obj.prop`.
>>
>> Invokes via instances and objects? It's never obvious at first look, if
>> that is a method execution, but it's surely a new invoke.
>>
>> If you've trapped once the result behind the scene, reading that, is just
>> noise for anyone eyes.
>>
>> So, once again, are we proposing something that results into exactly this?
>>
>> ```js
>> class Later {
>>   get thing() {
>>     return Object.defineProperty(this, 'thing', {value: anyLazy()});
>>   }
>>   constructor() {
>>     // always true, no matter when/where
>>     this.thing === this.thing;
>>   }
>> }
>> ```
>>
>> If so, I'm happy. If not, this is confusing and solving not much.
>>
>>
>> Best Regards
>>
>>
>> On Thu, Aug 31, 2017 at 9:14 PM, Isiah Meadows <isiahmeadows at gmail.com>
>> wrote:
>>
>>> Yes. I'll point out that having it as a function, rather than a
>>> property-specific thing, makes it more flexible, since you can define
>>> constants as lazy values (I do that in quite a few places).
>>>
>>> If you want to make it transparent, it's not that hard to make a
>>> single-line getter/method that hides the abstraction.
>>>
>>> Granted, most of my lazy values are properties, not constants, so I
>>> could consider it an acceptable compromise.
>>> -----
>>>
>>> Isiah Meadows
>>> me at isiahmeadows.com
>>>
>>> Looking for web consulting? Or a new website?
>>> Send me an email and we can get started.
>>> www.isiahmeadows.com
>>>
>>>
>>> On Thu, Aug 31, 2017 at 3:54 PM, Andrea Giammarchi
>>> <andrea.giammarchi at gmail.com> wrote:
>>> > so in JavaScript that results into this._db() each time, resolved
>>> lazily
>>> > with the first value returned once ?
>>> >
>>> > I still think my approach is cleaner and more transparent.
>>> >
>>> > `get _thing() { return defineProperty(this, 'thing', value) }`
>>> >
>>> > but if your TS-ish stuff translates into that, works for me
>>> >
>>> >
>>> >
>>> > On Thu, Aug 31, 2017 at 8:49 PM, Isiah Meadows <isiahmeadows at gmail.com
>>> >
>>> > wrote:
>>> >>
>>> >> It takes a function, and returns a function that (if necessary)
>>> >> initializes the value and then gets it.
>>> >> -----
>>> >>
>>> >> Isiah Meadows
>>> >> me at isiahmeadows.com
>>> >>
>>> >> Looking for web consulting? Or a new website?
>>> >> Send me an email and we can get started.
>>> >> www.isiahmeadows.com
>>> >>
>>> >>
>>> >> On Thu, Aug 31, 2017 at 3:43 PM, Andrea Giammarchi
>>> >> <andrea.giammarchi at gmail.com> wrote:
>>> >> > Sorry I don't speak TS, I speak ES.
>>> >> >
>>> >> > Can you please tell me in JavaScript what does that do?
>>> >> >
>>> >> > On Thu, Aug 31, 2017 at 8:18 PM, Isiah Meadows <
>>> isiahmeadows at gmail.com>
>>> >> > wrote:
>>> >> >>
>>> >> >> Note the TS-ish declaration above it. That's the variant I was
>>> >> >> referring to (I presented about 3 different variants initially).
>>> >> >>
>>> >> >> ```ts
>>> >> >> // The declaration I included
>>> >> >> declare function lazy<T>(init: () => T): () => T;
>>> >> >> ```
>>> >> >>
>>> >> >>
>>> >> >> On Thu, Aug 31, 2017 at 3:05 PM, Andrea Giammarchi
>>> >> >> <andrea.giammarchi at gmail.com> wrote:
>>> >> >> > it wouldn't work, would it ? I mean, you still have to pass
>>> through
>>> >> >> > the
>>> >> >> > "ugly" _db.get() thingy, right?
>>> >> >> >
>>> >> >> > how do you access and trigger the lazy bit within the class?
>>> >> >> >
>>> >> >> > On Thu, Aug 31, 2017 at 7:56 PM, Isiah Meadows
>>> >> >> > <isiahmeadows at gmail.com>
>>> >> >> > wrote:
>>> >> >> >>
>>> >> >> >> What about this (using the stage 3 class fields proposal)?
>>> >> >> >>
>>> >> >> >> ```js
>>> >> >> >> declare function lazy<T>(init: () => T): () => T;
>>> >> >> >>
>>> >> >> >> class WithLazyVals {
>>> >> >> >>     _db = lazy(() => new Promise(...));
>>> >> >> >> }
>>> >> >> >> ```
>>> >> >> >> -----
>>> >> >> >>
>>> >> >> >> Isiah Meadows
>>> >> >> >> me at isiahmeadows.com
>>> >> >> >>
>>> >> >> >> Looking for web consulting? Or a new website?
>>> >> >> >> Send me an email and we can get started.
>>> >> >> >> www.isiahmeadows.com
>>> >> >> >>
>>> >> >> >>
>>> >> >> >> On Thu, Aug 31, 2017 at 1:34 PM, Andrea Giammarchi
>>> >> >> >> <andrea.giammarchi at gmail.com> wrote:
>>> >> >> >> >> this proposal doesn't compose well with classes
>>> >> >> >> >
>>> >> >> >> > to expand a little, if you were proposing
>>> >> >> >> >
>>> >> >> >> > ```js
>>> >> >> >> > class WithLazyVals {
>>> >> >> >> >   lazy _db() { return new Promise(...); }
>>> >> >> >> > }
>>> >> >> >> > ```
>>> >> >> >> >
>>> >> >> >> > I would've taken first flight to come over and hug you.
>>> >> >> >> >
>>> >> >> >> > Best Regards
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> > On Thu, Aug 31, 2017 at 6:25 PM, Andrea Giammarchi
>>> >> >> >> > <andrea.giammarchi at gmail.com> wrote:
>>> >> >> >> >>
>>> >> >> >> >> > How often do you start out with a class like this ...
>>> >> >> >> >>
>>> >> >> >> >> Never, like I've said. This is the lazy pattern I know since
>>> >> >> >> >> ever.
>>> >> >> >> >>
>>> >> >> >> >> ```js
>>> >> >> >> >> class Foo {
>>> >> >> >> >>   get _db() {
>>> >> >> >> >>     return Object.defineProperty(this, '_db', {
>>> >> >> >> >>       value: new Promise((resolve, reject) => {
>>> >> >> >> >>         // open a database connection
>>> >> >> >> >>         // set up whatever tables you need to
>>> >> >> >> >>         // etc.
>>> >> >> >> >>       })
>>> >> >> >> >>     })._db;
>>> >> >> >> >>   }
>>> >> >> >> >> }
>>> >> >> >> >> ```
>>> >> >> >> >>
>>> >> >> >> >> Whenever you need, you just access `this._db`, no need to
>>> create
>>> >> >> >> >> an
>>> >> >> >> >> enumerable variable and a class method.
>>> >> >> >> >>
>>> >> >> >> >> It looks cleaner to me.
>>> >> >> >> >>
>>> >> >> >> >>
>>> >> >> >> >> > Things you don't want to initialize right away because
>>> >> >> >> >> > initialization
>>> >> >> >> >>
>>> >> >> >> >> You don't really have to convince me, I've written lazy
>>> >> >> >> >> properties
>>> >> >> >> >> since
>>> >> >> >> >> getters and setters were introduced [1]
>>> >> >> >> >>
>>> >> >> >> >> All I am saying is that this proposal doesn't compose well
>>> with
>>> >> >> >> >> classes,
>>> >> >> >> >> it's just yet another SuperPrimitive for the language.
>>> >> >> >> >>
>>> >> >> >> >> It is also something trivial to implement on user land, yet I
>>> >> >> >> >> haven't
>>> >> >> >> >> seen
>>> >> >> >> >> many writing code like the following:
>>> >> >> >> >>
>>> >> >> >> >> ```js
>>> >> >> >> >> function Lazy(fn) {
>>> >> >> >> >>   let c = false, v;
>>> >> >> >> >>   return {get(){ return c ? v : (c = !c, v = fn()) }};
>>> >> >> >> >> }
>>> >> >> >> >>
>>> >> >> >> >> var o = Lazy(() => Math.random());
>>> >> >> >> >> o.get(); // ...
>>> >> >> >> >> ```
>>> >> >> >> >>
>>> >> >> >> >> Maybe it's me that hasn't seen this widely adopted from some
>>> >> >> >> >> library?
>>> >> >> >> >>
>>> >> >> >> >> Anyway, this is just my opinion, maybe others would be happy
>>> with
>>> >> >> >> >> this.
>>> >> >> >> >>
>>> >> >> >> >> Best Regards
>>> >> >> >> >>
>>> >> >> >> >> [1] Class.lazy example
>>> >> >> >> >>
>>> >> >> >> >>
>>> >> >> >> >>
>>> >> >> >> >> https://github.com/WebReflection/prototypal/blob/master/Clas
>>> s.md#classlazycallback
>>> >> >> >> >>
>>> >> >> >> >>
>>> >> >> >> >>
>>> >> >> >> >> On Thu, Aug 31, 2017 at 6:03 PM, Isiah Meadows
>>> >> >> >> >> <isiahmeadows at gmail.com>
>>> >> >> >> >> wrote:
>>> >> >> >> >>>
>>> >> >> >> >>> It'd solve a problem similarly to Kotlin's `by lazy { ... }`
>>> >> >> >> >>> delegate,
>>> >> >> >> >>> .NET's `System.Lazy<T>`, Swift's `lazy var`, among many
>>> other
>>> >> >> >> >>> languages. It's very useful for lazy initialization [1],
>>> such as
>>> >> >> >> >>> lazily setting up a database, requesting a resource, among
>>> other
>>> >> >> >> >>> costly things. [2]
>>> >> >> >> >>>
>>> >> >> >> >>> How often do you start out with a class like this, where you
>>> >> >> >> >>> have
>>> >> >> >> >>> an
>>> >> >> >> >>> expensive resource you don't want to open right away?
>>> >> >> >> >>>
>>> >> >> >> >>> ```js
>>> >> >> >> >>> class Foo {
>>> >> >> >> >>>     constructor() {
>>> >> >> >> >>>         this._db = undefined
>>> >> >> >> >>>     }
>>> >> >> >> >>>
>>> >> >> >> >>>     _initDb() {
>>> >> >> >> >>>         if (this._db) return this._db
>>> >> >> >> >>>         return this._db = new Promise((resolve, reject) => {
>>> >> >> >> >>>             // open a database connection
>>> >> >> >> >>>             // set up whatever tables you need to
>>> >> >> >> >>>             // etc.
>>> >> >> >> >>>         })
>>> >> >> >> >>>     }
>>> >> >> >> >>> }
>>> >> >> >> >>> ```
>>> >> >> >> >>>
>>> >> >> >> >>> Or maybe, a large lookup table that takes a while to build,
>>> and
>>> >> >> >> >>> might
>>> >> >> >> >>> not even be used, so you don't want to do it on load?
>>> >> >> >> >>>
>>> >> >> >> >>> ```js
>>> >> >> >> >>> var table
>>> >> >> >> >>>
>>> >> >> >> >>> function initTable() {
>>> >> >> >> >>>     if (table) return
>>> >> >> >> >>>     table = new Array(10000)
>>> >> >> >> >>>     // do some expensive calculations
>>> >> >> >> >>> }
>>> >> >> >> >>> ```
>>> >> >> >> >>>
>>> >> >> >> >>> Things you don't want to initialize right away because
>>> >> >> >> >>> initialization
>>> >> >> >> >>> is expensive and/or the value might not even be used.
>>> That's the
>>> >> >> >> >>> problem I'm aiming to solve, and it's something I feel
>>> would be
>>> >> >> >> >>> useful
>>> >> >> >> >>> in its own right in the language, about equal in importance
>>> to
>>> >> >> >> >>> weak
>>> >> >> >> >>> references. (Slightly specialized, but the need is not
>>> >> >> >> >>> non-zero.)
>>> >> >> >> >>>
>>> >> >> >> >>> [1]: https://en.wikipedia.org/wiki/Lazy_initialization
>>> >> >> >> >>> [2]:
>>> >> >> >> >>>
>>> >> >> >> >>>
>>> >> >> >> >>>
>>> >> >> >> >>> https://stackoverflow.com/ques
>>> tions/978759/what-is-lazy-initialization-and-why-is-it-useful
>>> >> >> >> >>> -----
>>> >> >> >> >>>
>>> >> >> >> >>> Isiah Meadows
>>> >> >> >> >>> me at isiahmeadows.com
>>> >> >> >> >>>
>>> >> >> >> >>> Looking for web consulting? Or a new website?
>>> >> >> >> >>> Send me an email and we can get started.
>>> >> >> >> >>> www.isiahmeadows.com
>>> >> >> >> >>>
>>> >> >> >> >>>
>>> >> >> >> >>> On Thu, Aug 31, 2017 at 12:23 PM, Andrea Giammarchi
>>> >> >> >> >>> <andrea.giammarchi at gmail.com> wrote:
>>> >> >> >> >>> > right ... so ... I'm not sure I understand what this
>>> proposal
>>> >> >> >> >>> > would
>>> >> >> >> >>> > solve.
>>> >> >> >> >>> >
>>> >> >> >> >>> > Instead of this:
>>> >> >> >> >>> > ```js
>>> >> >> >> >>> > obj.val || (obj.val = getValue())
>>> >> >> >> >>> > ```
>>> >> >> >> >>> >
>>> >> >> >> >>> > you want to do this
>>> >> >> >> >>> > ```js
>>> >> >> >> >>> > (obj.val || (obj.val = new Lazy(getValue)).get();
>>> >> >> >> >>> > ```
>>> >> >> >> >>> >
>>> >> >> >> >>> > Where is the "win" and why is that?
>>> >> >> >> >>> >
>>> >> >> >> >>> >
>>> >> >> >> >>> >
>>> >> >> >> >>> > On Thu, Aug 31, 2017 at 5:18 PM, Isiah Meadows
>>> >> >> >> >>> > <isiahmeadows at gmail.com>
>>> >> >> >> >>> > wrote:
>>> >> >> >> >>> >>
>>> >> >> >> >>> >> With my proposed `Lazy` class, if you were to use an
>>> instance
>>> >> >> >> >>> >> as
>>> >> >> >> >>> >> a
>>> >> >> >> >>> >> descriptor, the `this` value it'd receive would not be a
>>> >> >> >> >>> >> `Lazy`
>>> >> >> >> >>> >> instance like it'd expect.
>>> >> >> >> >>> >>
>>> >> >> >> >>> >> Consider it the difference between `a.self` and
>>> `b.get()` in
>>> >> >> >> >>> >> your
>>> >> >> >> >>> >> example. `b.get()` is what I'd be expecting.
>>> >> >> >> >>> >> -----
>>> >> >> >> >>> >>
>>> >> >> >> >>> >> Isiah Meadows
>>> >> >> >> >>> >> me at isiahmeadows.com
>>> >> >> >> >>> >>
>>> >> >> >> >>> >> Looking for web consulting? Or a new website?
>>> >> >> >> >>> >> Send me an email and we can get started.
>>> >> >> >> >>> >> www.isiahmeadows.com
>>> >> >> >> >>> >>
>>> >> >> >> >>> >>
>>> >> >> >> >>> >> On Thu, Aug 31, 2017 at 12:12 PM, Andrea Giammarchi
>>> >> >> >> >>> >> <andrea.giammarchi at gmail.com> wrote:
>>> >> >> >> >>> >> >> using it in a descriptor would get it passed the wrong
>>> >> >> >> >>> >> >> `this`
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >> > sorry, what?
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >> > ```js
>>> >> >> >> >>> >> > var a = {};
>>> >> >> >> >>> >> > var b = {get() { return this; }};
>>> >> >> >> >>> >> > Object.defineProperty(a, 'self', b);
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >> > a.self === a; // true
>>> >> >> >> >>> >> > ```
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >> > On Thu, Aug 31, 2017 at 5:09 PM, Isiah Meadows
>>> >> >> >> >>> >> > <isiahmeadows at gmail.com>
>>> >> >> >> >>> >> > wrote:
>>> >> >> >> >>> >> >>
>>> >> >> >> >>> >> >> No. `Lazy` is intended to be an object to be used
>>> >> >> >> >>> >> >> directly,
>>> >> >> >> >>> >> >> not
>>> >> >> >> >>> >> >> a
>>> >> >> >> >>> >> >> descriptor of any kind.
>>> >> >> >> >>> >> >>
>>> >> >> >> >>> >> >> (My `lazy.get()` is an unbound method, so using it in
>>> a
>>> >> >> >> >>> >> >> descriptor
>>> >> >> >> >>> >> >> would get it passed the wrong `this`.)
>>> >> >> >> >>> >> >> -----
>>> >> >> >> >>> >> >>
>>> >> >> >> >>> >> >> Isiah Meadows
>>> >> >> >> >>> >> >> me at isiahmeadows.com
>>> >> >> >> >>> >> >>
>>> >> >> >> >>> >> >> Looking for web consulting? Or a new website?
>>> >> >> >> >>> >> >> Send me an email and we can get started.
>>> >> >> >> >>> >> >> www.isiahmeadows.com
>>> >> >> >> >>> >> >>
>>> >> >> >> >>> >> >>
>>> >> >> >> >>> >> >> On Thu, Aug 31, 2017 at 9:39 AM, Andrea Giammarchi
>>> >> >> >> >>> >> >> <andrea.giammarchi at gmail.com> wrote:
>>> >> >> >> >>> >> >> > the following is how I usually consider lazy values
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > ```js
>>> >> >> >> >>> >> >> > class Any {
>>> >> >> >> >>> >> >> >   _lazy(name) {
>>> >> >> >> >>> >> >> >     switch (name) {
>>> >> >> >> >>> >> >> >       case 'uid': return Math.random();
>>> >> >> >> >>> >> >> >       // others ... eventually
>>> >> >> >> >>> >> >> >     }
>>> >> >> >> >>> >> >> >   }
>>> >> >> >> >>> >> >> >   get uid() {
>>> >> >> >> >>> >> >> >     var value = this._lazy('uid');
>>> >> >> >> >>> >> >> >     // from now on, direct access
>>> >> >> >> >>> >> >> >     Object.defineProperty(this, 'uid', {value});
>>> >> >> >> >>> >> >> >     return value;
>>> >> >> >> >>> >> >> >   }
>>> >> >> >> >>> >> >> > }
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > const a = new Any;
>>> >> >> >> >>> >> >> > a.uid === a.uid; // true
>>> >> >> >> >>> >> >> > ```
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > If I understand correctly your proposal is to use
>>> Lazy
>>> >> >> >> >>> >> >> > as
>>> >> >> >> >>> >> >> > generic
>>> >> >> >> >>> >> >> > descriptor, is that correct ?
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > ```js
>>> >> >> >> >>> >> >> > Object.defineProperty({}, 'something', new
>>> Lazy(function
>>> >> >> >> >>> >> >> > (val)
>>> >> >> >> >>> >> >> > {
>>> >> >> >> >>> >> >> >   return this.shakaLaka ? val : 'no shakaLaka';
>>> >> >> >> >>> >> >> > }));
>>> >> >> >> >>> >> >> > ```
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > ???
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > If that's the case I see already people confused by
>>> >> >> >> >>> >> >> > arrow
>>> >> >> >> >>> >> >> > function
>>> >> >> >> >>> >> >> > in case they need to access the context,
>>> >> >> >> >>> >> >> > plus no property access optimization once resolved.
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > It's also not clear if such property can be set
>>> again
>>> >> >> >> >>> >> >> > later
>>> >> >> >> >>> >> >> > on
>>> >> >> >> >>> >> >> > (right
>>> >> >> >> >>> >> >> > now it
>>> >> >> >> >>> >> >> > cannot)
>>> >> >> >> >>> >> >> > 'cause lazy definition doesn't always necessarily
>>> mean
>>> >> >> >> >>> >> >> > inability
>>> >> >> >> >>> >> >> > to
>>> >> >> >> >>> >> >> > reassign.
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > What am I missing/misunderstanding?
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > Regards
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> > On Thu, Aug 31, 2017 at 2:21 PM, Isiah Meadows
>>> >> >> >> >>> >> >> > <isiahmeadows at gmail.com>
>>> >> >> >> >>> >> >> > wrote:
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> It'd be really nice if lazy values made it into the
>>> >> >> >> >>> >> >> >> spec
>>> >> >> >> >>> >> >> >> somehow.
>>> >> >> >> >>> >> >> >> I've
>>> >> >> >> >>> >> >> >> already found myself using things like this [1]
>>> quite a
>>> >> >> >> >>> >> >> >> bit,
>>> >> >> >> >>> >> >> >> and
>>> >> >> >> >>> >> >> >> I've
>>> >> >> >> >>> >> >> >> also found myself frequently initializing
>>> properties
>>> >> >> >> >>> >> >> >> not
>>> >> >> >> >>> >> >> >> on
>>> >> >> >> >>> >> >> >> first
>>> >> >> >> >>> >> >> >> access.
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> [1]:
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> https://gist.github.com/isiahm
>>> eadows/4c0723bdfa555a1c2cb01341b323c3d4
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> As for what would be a nice API, maybe something
>>> like
>>> >> >> >> >>> >> >> >> one
>>> >> >> >> >>> >> >> >> of
>>> >> >> >> >>> >> >> >> these?
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> ```js
>>> >> >> >> >>> >> >> >> class Lazy<T> {
>>> >> >> >> >>> >> >> >>     constructor(init: () => T);
>>> >> >> >> >>> >> >> >>     get(): T; // or error thrown
>>> >> >> >> >>> >> >> >> }
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> function lazy<T>(init: () => T): () => T; // or
>>> error
>>> >> >> >> >>> >> >> >> thrown
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> function lazy<T>(init: () => T): {
>>> >> >> >> >>> >> >> >>     get(): T; // or error thrown
>>> >> >> >> >>> >> >> >> }
>>> >> >> >> >>> >> >> >> ```
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> Alternatively, syntax might work, with `do`
>>> expression
>>> >> >> >> >>> >> >> >> semantics:
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> ```js
>>> >> >> >> >>> >> >> >> const x = lazy do { ... }
>>> >> >> >> >>> >> >> >> // expose via `x.get()` or just `x()`
>>> >> >> >> >>> >> >> >> ```
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> -----
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> Isiah Meadows
>>> >> >> >> >>> >> >> >> me at isiahmeadows.com
>>> >> >> >> >>> >> >> >>
>>> >> >> >> >>> >> >> >> Looking for web consulting? Or a new website?
>>> >> >> >> >>> >> >> >> Send me an email and we can get started.
>>> >> >> >> >>> >> >> >> www.isiahmeadows.com
>>> >> >> >> >>> >> >> >> _______________________________________________
>>> >> >> >> >>> >> >> >> es-discuss mailing list
>>> >> >> >> >>> >> >> >> es-discuss at mozilla.org
>>> >> >> >> >>> >> >> >> https://mail.mozilla.org/listinfo/es-discuss
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >> >
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >> >
>>> >> >> >> >>> >
>>> >> >> >> >>> >
>>> >> >> >> >>
>>> >> >> >> >>
>>> >> >> >> >
>>> >> >> >
>>> >> >> >
>>> >> >>
>>> >> >> -----
>>> >> >>
>>> >> >> Isiah Meadows
>>> >> >> me at isiahmeadows.com
>>> >> >>
>>> >> >> Looking for web consulting? Or a new website?
>>> >> >> Send me an email and we can get started.
>>> >> >> www.isiahmeadows.com
>>> >> >
>>> >> >
>>> >
>>> >
>>>
>>
>>
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss at mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>>
>
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