Obviously scoped, agreed, but again how would you allow scoped
initialization upon each iteration, or is it your preference not to allow
that? (again, initializers-as-expressions allows that, despite the other
concerns).
On Sun, 25 Mar 2018 at 10:57 Isiah Meadows <isiahmead...@gmail.com> wrote:
> 1. My concern with `while` is that it's a little too duplicative of
> C-style `for` functionally (although it's not an exact partial clone).
> That's why I backtracked on it right as I proposed it (within the same
> email).
> 2. The scope would have been just like `if`, where it's scoped to the
> body with an implicit inner block scope. Anything different would be
> surprising and unintuitive.
>
> -----
>
> Isiah Meadows
> m...@isiahmeadows.com
>
> Looking for web consulting? Or a new website?
> Send me an email and we can get started.
> www.isiahmeadows.com
>
>
> On Sun, Mar 25, 2018 at 12:55 AM, Naveen Chawla <naveen.c...@gmail.com>
> wrote:
> > I understand the fear about "bad code" potentially sprouting from it. I
> > guess I'm not as bothered as long as I can do what I want. So it's a
> matter
> > of how heavily weighted the "potential bad practice" concern is over
> > developer power.
> >
> > The advantage is that it's as powerful as the developer wants it to be,
> and
> > makes the common cases in `if` and `while` easy to learn and do.
> >
> > For example, you can do while( x > (const y = getYFromX(x) ) ), which
> none
> > of the other ideas directly allow.
> >
> > Which brings me to the next point. How would otherwise do this in a while
> > loop? I presume the while(;) based initialization part would only
> operate at
> > the start of the loop, to be consistent with for loops. So how would you
> > make a scoped variable initialization on every iteration?
> >
> > On Sun, 25 Mar 2018 at 03:21 Isiah Meadows <isiahmead...@gmail.com>
> wrote:
> >>
> >> I disagree, I feel it's too clever. It'd make sense in a control flow
> >> statement where in the alternate branch, the value is
> >> meaningless/useless/ineffable/etc. (and this is why `for` loops
> >> commonly allow such syntax already), but in ordinary function calls,
> >> it seems like it's just trying to golf the code without good reason.
> >>
> >> It's not visually ambiguous, just pointless in my opinion (a solution
> >> in search of a problem).
> >>
> >> -----
> >>
> >> Isiah Meadows
> >> m...@isiahmeadows.com
> >>
> >> Looking for web consulting? Or a new website?
> >> Send me an email and we can get started.
> >> www.isiahmeadows.com
> >>
> >>
> >> On Sat, Mar 24, 2018 at 7:54 AM, Naveen Chawla <naveen.c...@gmail.com>
> >> wrote:
> >> > I don't know why `foo(let x = 10)` would be a bad practice or hurt
> >> > readability.
> >> >
> >> > I find it perfectly readable and with obvious meaning!
> >> >
> >> > ```js
> >> > foo(const x = 10)
> >> > bar(x)
> >> > ```
> >> >
> >> > vs
> >> >
> >> > ```js
> >> > const x = 10
> >> > foo(x)
> >> > bar(x)
> >> > ```
> >> >
> >> > I also find it "clean". So I guess these aren't really useful terms.
> >> >
> >> > As for the `if(const x = 5)` being like `if(x = 5)` being confused
> with
> >> > `if(x==5)`, `if(const x == 5)` would throw an error anyway.
> >> >
> >> > On Fri, 23 Mar 2018 at 20:02 Rodrigo <rodrigol...@gmail.com> wrote:
> >> >>
> >> >> @Naveen, I think it's best to avoid this road altogether and keep
> >> >> initialization clean, even though assignment isn't.
> >> >>
> >> >> The proposal is that given `for(;;)` hence `if(;)` instead of given
> >> >> `x=y` hence `let x=y`.
> >> >>
> >> >> But yes, `if( x = 5)` is already allowed, but it's confusing and hard
> >> >> to
> >> >> read.
> >> >>
> >> >> Confusing on what is being compared on multiple statements:
> `if((const
> >> >> x = 5, y = 10) > 0)`
> >> >>
> >> >> Confusing when destructuring, on what's being compared: `if(let
> [x,y] =
> >> >> [1,2])`
> >> >>
> >> >> Confusing when multiple statements: `if ((x = 10, y = 20) > 15)`
> >> >>
> >> >> Looks like an error: `if( x = 5 )` versus `if( x == 5)`, did the
> >> >> programmer forget the `=`?
> >> >>
> >> >> And if you introduce nesting initializations everywhere outside the
> >> >> `if`, that's basically an invitation for readability nightmare. `let`
> >> >> and `const` anywhere introduce 2 conflicting best-practices:
> >> >>
> >> >> - Rule 1: declare your variables that are used exclusively within
> `if`
> >> >> blocks within the `if` parens
> >> >>
> >> >> - Rule 2: don't declare variables within another statement (so that
> >> >> people will refrain from doing `foo( let x=10 )`
> >> >>
> >> >> Consider that, historically, other languages such as Perl allowed
> `if(
> >> >> (my $x = 1) > 0)` and `foo( my $x = 100)` and became the ugly child
> of
> >> >> power programming; whereas Golang, born much later, has limited
> >> >> initializations to things such as `if( x:=1; x > 0)` and has kept
> >> >> things quite minimalistic (and clear for the programmer).
> >> >>
> >> >> ```perl
> >> >> # realworld example, hard to find variable declaration:
> >> >>
> >> >> $redis->subscribe( 'queue', my $callback = sub {
> >> >> ...
> >> >> });
> >> >> ```
> >> >>
> >> >>
> >> >> On Fri, Mar 23, 2018 at 7:21 AM, Naveen Chawla <
> naveen.c...@gmail.com>
> >> >> wrote:
> >> >> > I'm still not seeing a compelling case for not allowing `const` /
> >> >> > `let`
> >> >> > declarations to be evaluated as expressions. Or I've missed it.
> >> >> >
> >> >> > As was noted,
> >> >> >
> >> >> > `if(x = 5)` is already allowed.
> >> >> >
> >> >> > Is `if(const x = 5)` really that much of a stretch?
> >> >> >
> >> >> > To answer a concern about a function call like `myFunction(const x
> =
> >> >> > 7)`, of
> >> >> > course the scope of `x` would be where it is declared. It can't be
> >> >> > anywhere
> >> >> > else (like inside myFunction or something).
> >> >> >
> >> >> > On Thu, 22 Mar 2018 at 22:53 Isiah Meadows <isiahmead...@gmail.com
> >
> >> >> > wrote:
> >> >> >>
> >> >> >> Probably true, more so than the `if (var ...)`/etc. (which can't
> be
> >> >> >> as
> >> >> >> easily desugared). My `else` variant desugars more to something
> that
> >> >> >> is also easily simulated, and it's a less common case:
> >> >> >>
> >> >> >> ```js
> >> >> >> let foo = bar else return baz;
> >> >> >>
> >> >> >> // Desugared
> >> >> >> let _tmp = bar;
> >> >> >> if (tmp == null) return baz;
> >> >> >> let foo = _tmp;
> >> >> >> ```
> >> >> >>
> >> >> >> In this case, there's also the question of whether to require a
> >> >> >> `return` in all code paths, which probably makes this a bit more
> >> >> >> complicated than what would be worth for such a simple language
> >> >> >> feature.
> >> >> >> -----
> >> >> >>
> >> >> >> Isiah Meadows
> >> >> >> m...@isiahmeadows.com
> >> >> >>
> >> >> >> Looking for web consulting? Or a new website?
> >> >> >> Send me an email and we can get started.
> >> >> >> www.isiahmeadows.com
> >> >> >>
> >> >> >>
> >> >> >> On Thu, Mar 22, 2018 at 12:23 PM, Michael Luder-Rosefield
> >> >> >> <rosyatran...@gmail.com> wrote:
> >> >> >> > That strikes me as territory the 'do expression' proposal
> >> >> >> > https://github.com/tc39/proposal-do-expressions is more fitted
> >> >> >> > for:
> >> >> >> >
> >> >> >> > const x = do { if (c) expr; else { ... } };
> >> >> >> >
> >> >> >> > What I'd like for this proposal is something that works
> >> >> >> > consistently
> >> >> >> > and
> >> >> >> > obviously for all blocks with a parenthesised element to them.
> >> >> >> > When
> >> >> >> > they're
> >> >> >> > formally separated by semi-colons, as in `for (a;b;c)`, each of
> >> >> >> > `a,b,c`
> >> >> >> > acts
> >> >> >> > as an expression. Why not allow any of those expressions to be
> >> >> >> > replaced
> >> >> >> > by a
> >> >> >> > statement block that acts like a do expression, each of which's
> >> >> >> > scope
> >> >> >> > is
> >> >> >> > nested under the previous one and are available to the following
> >> >> >> > block?
> >> >> >> >
> >> >> >> > That didn't come out very clearly, so let's try with an example:
> >> >> >> >
> >> >> >> > for ({
> >> >> >> > let x = 1, y = 2;
> >> >> >> > console.log("I'll be printed every loop!");
> >> >> >> > }; {
> >> >> >> > let s = 'some string';
> >> >> >> > if (y%7 === 0) x === y;
> >> >> >> > else x < 1000;
> >> >> >> > }; {
> >> >> >> > let s = 'some other string';
> >> >> >> > x+=1;
> >> >> >> > if (y%3 === 0) y += 2;
> >> >> >> > else y += 1;
> >> >> >> > }) {
> >> >> >> > // whatever code here
> >> >> >> > // local scope hierarchy is
> >> >> >> > // {
> >> >> >> > // x,
> >> >> >> > // y,
> >> >> >> > // __SCOPE__: {
> >> >> >> > // s: 'some string',
> >> >> >> > // __SCOPE__: {
> >> >> >> > // s: 'some other string'
> >> >> >> > // }
> >> >> >> > // }
> >> >> >> > // }
> >> >> >> > }
> >> >> >> >
> >> >> >> > I'm just using some random logic in the blocks to illustrate the
> >> >> >> > point:
> >> >> >> > all
> >> >> >> > the variables declared in the blocks are accessible in the for
> >> >> >> > block,
> >> >> >> > but
> >> >> >> > the 'some string' `s` is masked by the 'some other string' `s`
> in
> >> >> >> > the
> >> >> >> > child
> >> >> >> > scope. The termination condition in the second block can vary
> each
> >> >> >> > loop,
> >> >> >> > as
> >> >> >> > can the iteration operation in the last block, and is simply the
> >> >> >> > last
> >> >> >> > value
> >> >> >> > in the block as-per do expressions.
> >> >> >> >
> >> >> >> > On Thu, 22 Mar 2018 at 15:44 Mike Samuel <mikesam...@gmail.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> On Thu, Mar 22, 2018 at 3:50 AM, Isiah Meadows
> >> >> >> >> <isiahmead...@gmail.com>
> >> >> >> >> wrote:
> >> >> >> >>>
> >> >> >> >>>
> >> >> >> >>> I do have one other related thing I'd like to see: add a `let
> >> >> >> >>> foo =
> >> >> >> >>> expr() else { ... }` variant, with a line terminator
> restriction
> >> >> >> >>> before the `else` so it can't be confused with an `else`
> within
> >> >> >> >>> an
> >> >> >> >>> `if`.
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> Making it a restricted production would solve the grammatical
> >> >> >> >> ambiguity
> >> >> >> >> for existing code, but maybe in an errorprone way for future
> >> >> >> >> code:
> >> >> >> >>
> >> >> >> >> if (c) let foo = expr() else { ... } // else attaches to
> let
> >> >> >> >> if (c) let foo = expr(); else { ... } // else attaches to
> if
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> Would the semantics differ from
> >> >> >> >>
> >> >> >> >> let foo = expr() || ({} => { ... })()
> >> >> >> >>
> >> >> >> >> ?
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>>
> >> >> >> >>>
> >> >> >> >>> -----
> >> >> >> >>>
> >> >> >> >>> Isiah Meadows
> >> >> >> >>> m...@isiahmeadows.com
> >> >> >> >>>
> >> >> >> >>> Looking for web consulting? Or a new website?
> >> >> >> >>> Send me an email and we can get started.
> >> >> >> >>> www.isiahmeadows.com
> >> >> >> >>>
> >> >> >> >>>
> >> >> >> >>> On Thu, Mar 22, 2018 at 3:21 AM, Rodrigo <
> rodrigol...@gmail.com>
> >> >> >> >>> wrote:
> >> >> >> >>> > Not just let-scopes, but the introduction of `async/await`
> >> >> >> >>> > also
> >> >> >> >>> > welcomes the introduction of if-scoped variables.
> >> >> >> >>> >
> >> >> >> >>> > if (const data = await collection.find({}).toArray();
> >> >> >> >>> > data.length >
> >> >> >> >>> > 10)
> >> >> >> >>> > {
> >> >> >> >>> > console.log(data);
> >> >> >> >>> > } else if (data.length > 0) {
> >> >> >> >>> > console.log(data);
> >> >> >> >>> > } else {
> >> >> >> >>> > console.log(data);
> >> >> >> >>> > }
> >> >> >> >>> >
> >> >> >> >>> > And, as mentioned by @jerry, this can be extended to
> `switch`
> >> >> >> >>> > and
> >> >> >> >>> > `while`. Golang has `switch(;)` initialization too afaik.
> >> >> >> >>> >
> >> >> >> >>> > switch( const today = new Date(); today.getDay() ) {
> >> >> >> >>> > case 0:
> >> >> >> >>> > console.log( "Don't work on %s",
> today.toString()
> >> >> >> >>> > );
> >> >> >> >>> > break;
> >> >> >> >>> > }
> >> >> >> >>> >
> >> >> >> >>> > `while` would be a bit unnecessary, due to the fact that it
> >> >> >> >>> > can
> >> >> >> >>> > be
> >> >> >> >>> > replicated with `for( <assign>; <expression>; )`, but could
> be
> >> >> >> >>> > available for consistency with `if` and `switch`.
> >> >> >> >>> >
> >> >> >> >>> > El mié., 21 mar. 2018 19:47, Mike Samuel
> >> >> >> >>> > <mikesam...@gmail.com>
> >> >> >> >>> > escribió:
> >> >> >> >>> >>
> >> >> >> >>> >>
> >> >> >> >>> >>
> >> >> >> >>> >> On Wed, Mar 21, 2018 at 1:27 PM, Sebastian Malton
> >> >> >> >>> >> <sebast...@malton.name>
> >> >> >> >>> >> wrote:
> >> >> >> >>> >>>
> >> >> >> >>> >>> Because block-level scoping is a very good way to avoid
> >> >> >> >>> >>> certain
> >> >> >> >>> >>> bugs
> >> >> >> >>> >>> and
> >> >> >> >>> >>> is easier to reason about. Especially when considering
> >> >> >> >>> >>> project
> >> >> >> >>> >>> successors.
> >> >> >> >>> >>
> >> >> >> >>> >>
> >> >> >> >>> >> +1. function-scoped variables in loop bodies caused tons
> of
> >> >> >> >>> >> bugs
> >> >> >> >>> >> before
> >> >> >> >>> >> let-scoped variables and were a main motivating case.
> >> >> >> >>> >>
> >> >> >> >>> >> var i;
> >> >> >> >>> >> for (i = 0; i < arr.length; ++i) {
> >> >> >> >>> >> f(function () { /* Do something with */ arr[i]; });
> >> >> >> >>> >> }
> >> >> >> >>> >>
> >> >> >> >>> >> vs
> >> >> >> >>> >>
> >> >> >> >>> >> for (let i = 0; i < arr.length; ++i) {
> >> >> >> >>> >> f(function () { /* Do something with */ arr[i]; });
> >> >> >> >>> >> }
> >> >> >> >>> >>
> >> >> >> >>> >> Yes, linters got pretty good at finding uses of closed-over
> >> >> >> >>> >> variables
> >> >> >> >>> >> modified in a loop, but the workarounds were not ideal.
> >> >> >> >>> >>
> >> >> >> >>> >> var i;
> >> >> >> >>> >> for (i = 0; i < arr.length; ++i) {
> >> >> >> >>> >> f(function (i) { return function () { /* Do something
> with
> >> >> >> >>> >> */
> >> >> >> >>> >> arr[i]; }
> >> >> >> >>> >> }(i));
> >> >> >> >>> >> }
> >> >> >> >>> >>
> >> >> >> >>> >> Block scoping is just better for code that uses loops,
> >> >> >> >>> >> variables,
> >> >> >> >>> >> and
> >> >> >> >>> >> function expressions.
> >> >> >> >>> >>
> >> >> >> >>> >> _______________________________________________
> >> >> >> >>> >> es-discuss mailing list
> >> >> >> >>> >> es-discuss@mozilla.org
> >> >> >> >>> >> https://mail.mozilla.org/listinfo/es-discuss
> >> >> >> >>> >
> >> >> >> >>> >
> >> >> >> >>> > _______________________________________________
> >> >> >> >>> > es-discuss mailing list
> >> >> >> >>> > es-discuss@mozilla.org
> >> >> >> >>> > https://mail.mozilla.org/listinfo/es-discuss
> >> >> >> >>> >
> >> >> >> >>
> >> >> >> >> _______________________________________________
> >> >> >> >> es-discuss mailing list
> >> >> >> >> es-discuss@mozilla.org
> >> >> >> >> https://mail.mozilla.org/listinfo/es-discuss
> >> >> >> _______________________________________________
> >> >> >> es-discuss mailing list
> >> >> >> es-discuss@mozilla.org
> >> >> >> https://mail.mozilla.org/listinfo/es-discuss
> >> >> >
> >> >> >
> >> >> > _______________________________________________
> >> >> > es-discuss mailing list
> >> >> > es-discuss@mozilla.org
> >> >> > https://mail.mozilla.org/listinfo/es-discuss
> >> >> >
>
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