Re: Re: Strict Relational Operators

[Darien Valentine]

> It's reasonable for non-coercing === to work on different types, but what
would a non-coercing + do with different types? It has to throw an error.

Ah, didn’t catch that you were talking about non-relational operators as
well. Assuming a strict `+` was still overloaded for string concatenation,
yeah, an error makes sense (whereas if numeric only, NaN might also be
considered a reasonable answer).

For strict `<`, etc, I think it would be unintuitive to get an error or to
have arbitrary type order. Rather I’d expect it to be false when the types
didn’t match, since, for example, the correct answer to both the questions
"is seven greater than an object?" and "is an object greater than 7?" is
"no". This would be consistent with the behavior of the existing
always-incomparable value, NaN, as well. That said, I think an error would
be better than having an arbitrary type order if those were the two choices.

On Thu, Apr 13, 2017 at 12:56 AM, felix  wrote:

> On Wed, Apr 12, 2017 at 7:23 PM, Darien Valentine 
> wrote:
> >> One common JS problem is NaNs ending up in unexpected places, and it's
> >> often difficult to trace back where they came from. Getting a type error
> >> instead of a NaN would be nice.
> >
> > I’m not sure this would help with that. NaN may be the product of
> coercion,
> > but NaN itself is a numeric value, and it can be produced without any
> type
> > coercion, e.g. `Infinity/Infinity`, `(-1) ** 0.5`, etc. And the `===`
> > operator is a strict, non-coercive comparison, but that doesn’t mean it
> > throws type errors.
>
> Mysterious NaNs in js are usually due to implicit conversion of random
> objects to numbers, not normal numeric computation.
>
> It's reasonable for non-coercing === to work on different types, but
> what would a non-coercing + do with different types? It has to throw
> an error.
>
> Non-coercing < might throw an error or use some arbitrary ordering of
> types. I don't have strong feelings about that.
>
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Re: Re: Strict Relational Operators

[felix]

On Wed, Apr 12, 2017 at 7:23 PM, Darien Valentine  wrote:
>> One common JS problem is NaNs ending up in unexpected places, and it's
>> often difficult to trace back where they came from. Getting a type error
>> instead of a NaN would be nice.
>
> I’m not sure this would help with that. NaN may be the product of coercion,
> but NaN itself is a numeric value, and it can be produced without any type
> coercion, e.g. `Infinity/Infinity`, `(-1) ** 0.5`, etc. And the `===`
> operator is a strict, non-coercive comparison, but that doesn’t mean it
> throws type errors.

Mysterious NaNs in js are usually due to implicit conversion of random
objects to numbers, not normal numeric computation.

It's reasonable for non-coercing === to work on different types, but
what would a non-coercing + do with different types? It has to throw
an error.

Non-coercing < might throw an error or use some arbitrary ordering of
types. I don't have strong feelings about that.
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Re: Re: Strict Relational Operators

[Darien Valentine]

> One common JS problem is NaNs ending up in unexpected places, and it's often
difficult to trace back where they came from. Getting a type error instead
of a NaN would be nice.

I’m not sure this would help with that. NaN may be the product of coercion,
but NaN itself is a numeric value, and it can be produced without any type
coercion, e.g. `Infinity/Infinity`, `(-1) ** 0.5`, etc. And the `===`
operator is a strict, non-coercive comparison, but that doesn’t mean it
throws type errors.

On Wed, Apr 12, 2017 at 7:48 PM, felix  wrote:

> One common JS problem is NaNs ending up in unexpected places, and it's
> often difficult to trace back where they came from. Getting a type
> error instead of a NaN would be nice.
>
> I think this is a reasonable argument for being able to write
> expressions with non-coercing operators, and this is why I'd lean
> toward annotating an entire expression as non-coercing, instead of
> doubling the number of operators.
>
> On Wed, Apr 12, 2017 at 9:25 AM, T.J. Crowder
>  wrote:
> > FWIW, I think the next steps for this discussion are:
> >
> > 1. To hear from people whether they feel the need for these operations in
> > their everyday work. It's interesting, you so often hear people saying
> > "Always use `===`, not `==`!" with...fervor...but apparently strict
> versions
> > of the relational operators aren't (or weren't) on people's minds. :-)
> >
> > 2. To hear from implementers about the difficulty level of adding four
> more
> > symbolic operators (`<=<`, `<==`, `>=>`, and `>==` or whatever they end
> up
> > being).
> >
> > (I like my non-symbolic operators -- `lt`, `lte`, and such -- but I doubt
> > they'd pass muster, for the reasons Brendan flagged up in the thread
> about
> > infix functions.)
> >
> > If the answer to #1 is "meh," discussions of operators vs. functions is
> > moot; nothing's going to happen. If the answer to #1 is "Oh yes, this
> would
> > be really useful" and the answer to #2 is "Fairly straightforward",
> that's a
> > solid steer as well, as is a "Actually, surprisingly hard" to #2 (and it
> > would be surprising, at least to me, but what do I know about
> implementing a
> > JavaScript engine).
> >
> > -- T.J. Crowder
> >
> > On Wed, Apr 12, 2017 at 4:49 PM, Michael J. Ryan 
> wrote:
> >>
> >> That's part of why I suggested it... My mention of Object.* Was mainly
> >> that it could defer to a common base class/constructor implementation
> for
> >> comparison.  And that a string and number implementation should be
> >> provided...
> >>
> >> I'm also good with having non-matching types return undefined while
> >> matching types is a Boolean.
> >>
> >> Object.* could just defer to the prototype implementation of the first
> >> value.. null or undefined always returning undefined.
> >>
> >> --
> >> Michael J. Ryan - track...@gmail.com - http://tracker1.info
> >>
> >> Please excuse grammar errors and typos, as this message was sent from my
> >> phone.
> >>
> >> On Apr 12, 2017 7:04 AM, "Darien Valentine" 
> wrote:
> >>>
> >>> > Personally I think `a < b` should just become a compile error if the
> >>> > types are not number.
> >>>
> >>> Breaking stuff aside, I think this is an important point. The fact that
> >>> the LT/GT operators do work on strings is a source of bugs. As with
> default
> >>> sort, I’ve seen code written a number of times where it was evident the
> >>> author expected the behavior would be more like
> >>> `Intl.Collator.prototype.compare`.
> >>>
> >>> Unless I’m missing some important common use case for comparing strings
> >>> based on byte values (`assert('a' > 'B')`), I think `Number.gt`,
> >>> `Number.gte`, `Number.lt`, `Number.lte` would be a good solution.
> >>>
> >>> On Wed, Apr 12, 2017 at 5:09 AM, T.J. Crowder
> >>>  wrote:
> 
>  > Personally I think `a < b` should just become a compile error if the
>  > types are not number. TypeScript?
> 
>  I'm not following you. JavaScript variables don't have types, so it
>  can't become a compile-time error; and making it one would
> *massively* break
>  the web. (Yes, you can use TypeScript to get types if you like, but
> we're
>  not talking about TypeScript.)
> 
>  > ...that's a separable concern which should not be part of the
>  > operator's behaviour IMO...
> 
>  There's no talk of changing how `<` and `>` (or `<=` and `>=`) work.
> 
>  But just as we have `==` (loose, coercing) and `===` (strict,
>  non-coercing), the discussion is about having strict non-coercing
> versions
>  of `<`, `>`, `<=`, and `>=`.
> 
>  -- T.J. Crowder
> 
> 
>  On Wed, Apr 12, 2017 at 10:00 AM, Alexander Jones 
> wrote:
> >
> > Personally I think `a < b` should just become a compile error if the
> > types are not number. TypeScript?
> >
> > If you want to 

Re: Re: Strict Relational Operators

[felix]

One common JS problem is NaNs ending up in unexpected places, and it's
often difficult to trace back where they came from. Getting a type
error instead of a NaN would be nice.

I think this is a reasonable argument for being able to write
expressions with non-coercing operators, and this is why I'd lean
toward annotating an entire expression as non-coercing, instead of
doubling the number of operators.

On Wed, Apr 12, 2017 at 9:25 AM, T.J. Crowder
 wrote:
> FWIW, I think the next steps for this discussion are:
>
> 1. To hear from people whether they feel the need for these operations in
> their everyday work. It's interesting, you so often hear people saying
> "Always use `===`, not `==`!" with...fervor...but apparently strict versions
> of the relational operators aren't (or weren't) on people's minds. :-)
>
> 2. To hear from implementers about the difficulty level of adding four more
> symbolic operators (`<=<`, `<==`, `>=>`, and `>==` or whatever they end up
> being).
>
> (I like my non-symbolic operators -- `lt`, `lte`, and such -- but I doubt
> they'd pass muster, for the reasons Brendan flagged up in the thread about
> infix functions.)
>
> If the answer to #1 is "meh," discussions of operators vs. functions is
> moot; nothing's going to happen. If the answer to #1 is "Oh yes, this would
> be really useful" and the answer to #2 is "Fairly straightforward", that's a
> solid steer as well, as is a "Actually, surprisingly hard" to #2 (and it
> would be surprising, at least to me, but what do I know about implementing a
> JavaScript engine).
>
> -- T.J. Crowder
>
> On Wed, Apr 12, 2017 at 4:49 PM, Michael J. Ryan  wrote:
>>
>> That's part of why I suggested it... My mention of Object.* Was mainly
>> that it could defer to a common base class/constructor implementation for
>> comparison.  And that a string and number implementation should be
>> provided...
>>
>> I'm also good with having non-matching types return undefined while
>> matching types is a Boolean.
>>
>> Object.* could just defer to the prototype implementation of the first
>> value.. null or undefined always returning undefined.
>>
>> --
>> Michael J. Ryan - track...@gmail.com - http://tracker1.info
>>
>> Please excuse grammar errors and typos, as this message was sent from my
>> phone.
>>
>> On Apr 12, 2017 7:04 AM, "Darien Valentine"  wrote:
>>>
>>> > Personally I think `a < b` should just become a compile error if the
>>> > types are not number.
>>>
>>> Breaking stuff aside, I think this is an important point. The fact that
>>> the LT/GT operators do work on strings is a source of bugs. As with default
>>> sort, I’ve seen code written a number of times where it was evident the
>>> author expected the behavior would be more like
>>> `Intl.Collator.prototype.compare`.
>>>
>>> Unless I’m missing some important common use case for comparing strings
>>> based on byte values (`assert('a' > 'B')`), I think `Number.gt`,
>>> `Number.gte`, `Number.lt`, `Number.lte` would be a good solution.
>>>
>>> On Wed, Apr 12, 2017 at 5:09 AM, T.J. Crowder
>>>  wrote:

 > Personally I think `a < b` should just become a compile error if the
 > types are not number. TypeScript?

 I'm not following you. JavaScript variables don't have types, so it
 can't become a compile-time error; and making it one would *massively* 
 break
 the web. (Yes, you can use TypeScript to get types if you like, but we're
 not talking about TypeScript.)

 > ...that's a separable concern which should not be part of the
 > operator's behaviour IMO...

 There's no talk of changing how `<` and `>` (or `<=` and `>=`) work.

 But just as we have `==` (loose, coercing) and `===` (strict,
 non-coercing), the discussion is about having strict non-coercing versions
 of `<`, `>`, `<=`, and `>=`.

 -- T.J. Crowder


 On Wed, Apr 12, 2017 at 10:00 AM, Alexander Jones  wrote:
>
> Personally I think `a < b` should just become a compile error if the
> types are not number. TypeScript?
>
> If you want to also check that they are both number (that's surely what
> we mean here and not that they are both string!) and return `false` if 
> not,
> that's a separable concern which should not be part of the operator's
> behaviour IMO. It would appear to just mask fundamental typing errors,
> unless I am missing some perspective?
>
> Alex
>
> On Wed, 12 Apr 2017 at 09:02, T.J. Crowder
>  wrote:
>>
>> Grr, there's always something. I forgot to mention that solving this
>> with functions is an option because short-circuiting isn't an issue, both
>> operands have to be evaluated by these relational operators anyway. So
>> unlike the motiviations for infix functions or macros or whatever, we 

Re: Re: Strict Relational Operators

[T.J. Crowder]

FWIW, I think the next steps for this discussion are:

1. To hear from people whether they feel the need for these operations in
their everyday work. It's interesting, you so often hear people saying
"Always use `===`, not `==`!" with...fervor...but apparently strict
versions of the relational operators aren't (or weren't) on people's minds.
:-)

2. To hear from implementers about the difficulty level of adding four more
symbolic operators (`<=<`, `<==`, `>=>`, and `>==` or whatever they end up
being).

(I like my non-symbolic operators -- `lt`, `lte`, and such -- but I doubt
they'd pass muster, for the reasons Brendan flagged up in the thread about
infix functions.)

If the answer to #1 is "meh," discussions of operators vs. functions is
moot; nothing's going to happen. If the answer to #1 is "Oh yes, this would
be really useful" and the answer to #2 is "Fairly straightforward", that's
a solid steer as well, as is a "Actually, surprisingly hard" to #2 (and it
would be surprising, at least to me, but what do I know about implementing
a JavaScript engine).

-- T.J. Crowder

On Wed, Apr 12, 2017 at 4:49 PM, Michael J. Ryan  wrote:

> That's part of why I suggested it... My mention of Object.* Was mainly
> that it could defer to a common base class/constructor implementation for
> comparison.  And that a string and number implementation should be
> provided...
>
> I'm also good with having non-matching types return undefined while
> matching types is a Boolean.
>
> Object.* could just defer to the prototype implementation of the first
> value.. null or undefined always returning undefined.
>
> --
> Michael J. Ryan - track...@gmail.com - http://tracker1.info
>
> Please excuse grammar errors and typos, as this message was sent from my
> phone.
>
> On Apr 12, 2017 7:04 AM, "Darien Valentine"  wrote:
>
>> > Personally I think `a < b` should just become a compile error if the
>> types are not number.
>>
>> Breaking stuff aside, I think this is an important point. The fact that
>> the LT/GT operators do work on strings is a source of bugs. As with default
>> sort, I’ve seen code written a number of times where it was evident the
>> author expected the behavior would be more like
>> `Intl.Collator.prototype.compare`.
>>
>> Unless I’m missing some important common use case for comparing strings
>> based on byte values (`assert('a' > 'B')`), I think `Number.gt`,
>> `Number.gte`, `Number.lt`, `Number.lte` would be a good solution.
>>
>> On Wed, Apr 12, 2017 at 5:09 AM, T.J. Crowder <
>> tj.crow...@farsightsoftware.com> wrote:
>>
>>> > Personally I think `a < b` should just become a compile error if the
>>> types are not number. TypeScript?
>>>
>>> I'm not following you. JavaScript variables don't have types, so it
>>> can't become a compile-time error; and making it one would *massively*
>>> break the web. (Yes, you can use TypeScript to get types if you like, but
>>> we're not talking about TypeScript.)
>>>
>>> > ...that's a separable concern which should not be part of the
>>> operator's behaviour IMO...
>>>
>>> There's no talk of changing how `<` and `>` (or `<=` and `>=`) work.
>>>
>>> But just as we have `==` (loose, coercing) and `===` (strict,
>>> non-coercing), the discussion is about having strict non-coercing versions
>>> of `<`, `>`, `<=`, and `>=`.
>>>
>>> -- T.J. Crowder
>>>
>>>
>>> On Wed, Apr 12, 2017 at 10:00 AM, Alexander Jones  wrote:
>>>
 Personally I think `a < b` should just become a compile error if the
 types are not number. TypeScript?

 If you want to also check that they are both number (that's surely what
 we mean here and not that they are both string!) and return `false` if not,
 that's a separable concern which should not be part of the operator's
 behaviour IMO. It would appear to just mask fundamental typing errors,
 unless I am missing some perspective?

 Alex

 On Wed, 12 Apr 2017 at 09:02, T.J. Crowder <
 tj.crow...@farsightsoftware.com> wrote:

> Grr, there's always something. I forgot to mention that solving this
> with functions is an option because short-circuiting isn't an issue, both
> operands have to be evaluated by these relational operators anyway. So
> unlike the motiviations for infix functions or macros or whatever, we 
> don't
> have that issue here.
>
> -- T.J. Crowder
>
>
> On Wed, Apr 12, 2017 at 8:56 AM, T.J. Crowder <
> tj.crow...@farsightsoftware.com> wrote:
>
> Very interesting stuff so far.
>
> My take on some options, organized into sections:
>
> * Solving it in userland
> * Using symbolic operators
> * Using functions
> * Using non-symbolic operators
>
> # Solving it in userland:
>
> Anyone wanting strict relational operators today can readily give
> themselves functions for it:
>
> ```js
> const lt = (a, b) => typeof a === typeof b 

Re: Re: Strict Relational Operators

[Michael J. Ryan]

That's part of why I suggested it... My mention of Object.* Was mainly that
it could defer to a common base class/constructor implementation for
comparison.  And that a string and number implementation should be
provided...

I'm also good with having non-matching types return undefined while
matching types is a Boolean.

Object.* could just defer to the prototype implementation of the first
value.. null or undefined always returning undefined.

-- 
Michael J. Ryan - track...@gmail.com - http://tracker1.info

Please excuse grammar errors and typos, as this message was sent from my
phone.

On Apr 12, 2017 7:04 AM, "Darien Valentine"  wrote:

> > Personally I think `a < b` should just become a compile error if the
> types are not number.
>
> Breaking stuff aside, I think this is an important point. The fact that
> the LT/GT operators do work on strings is a source of bugs. As with default
> sort, I’ve seen code written a number of times where it was evident the
> author expected the behavior would be more like `Intl.Collator.prototype.
> compare`.
>
> Unless I’m missing some important common use case for comparing strings
> based on byte values (`assert('a' > 'B')`), I think `Number.gt`,
> `Number.gte`, `Number.lt`, `Number.lte` would be a good solution.
>
> On Wed, Apr 12, 2017 at 5:09 AM, T.J. Crowder <
> tj.crow...@farsightsoftware.com> wrote:
>
>> > Personally I think `a < b` should just become a compile error if the
>> types are not number. TypeScript?
>>
>> I'm not following you. JavaScript variables don't have types, so it can't
>> become a compile-time error; and making it one would *massively* break the
>> web. (Yes, you can use TypeScript to get types if you like, but we're not
>> talking about TypeScript.)
>>
>> > ...that's a separable concern which should not be part of the
>> operator's behaviour IMO...
>>
>> There's no talk of changing how `<` and `>` (or `<=` and `>=`) work.
>>
>> But just as we have `==` (loose, coercing) and `===` (strict,
>> non-coercing), the discussion is about having strict non-coercing versions
>> of `<`, `>`, `<=`, and `>=`.
>>
>> -- T.J. Crowder
>>
>>
>> On Wed, Apr 12, 2017 at 10:00 AM, Alexander Jones  wrote:
>>
>>> Personally I think `a < b` should just become a compile error if the
>>> types are not number. TypeScript?
>>>
>>> If you want to also check that they are both number (that's surely what
>>> we mean here and not that they are both string!) and return `false` if not,
>>> that's a separable concern which should not be part of the operator's
>>> behaviour IMO. It would appear to just mask fundamental typing errors,
>>> unless I am missing some perspective?
>>>
>>> Alex
>>>
>>> On Wed, 12 Apr 2017 at 09:02, T.J. Crowder <
>>> tj.crow...@farsightsoftware.com> wrote:
>>>
 Grr, there's always something. I forgot to mention that solving this
 with functions is an option because short-circuiting isn't an issue, both
 operands have to be evaluated by these relational operators anyway. So
 unlike the motiviations for infix functions or macros or whatever, we don't
 have that issue here.

 -- T.J. Crowder


 On Wed, Apr 12, 2017 at 8:56 AM, T.J. Crowder <
 tj.crow...@farsightsoftware.com> wrote:

 Very interesting stuff so far.

 My take on some options, organized into sections:

 * Solving it in userland
 * Using symbolic operators
 * Using functions
 * Using non-symbolic operators

 # Solving it in userland:

 Anyone wanting strict relational operators today can readily give
 themselves functions for it:

 ```js
 const lt = (a, b) => typeof a === typeof b && a < b;
 ```

 Usage:

 ```js
 if (lt(a, b)) {
 // ...
 }
 ```

 So the question is whether the value of having a standard way of
 expressing this is worth the cost of adding it?

 Playing into that is that various options come with varying costs:

 * Using symbolic operators has a cost, but doesn't change fundamentals;
 I'm not an implementer, but I'd think the cost would be fairly low (but
 non-zero). *Any* syntax change rattles parsing cages everywhere, but syntax
 changes are now fairly regular occurrences in JavaScript.
 * Using functions means no new syntax, which means not rattling parsing
 cages, and are polyfillable.
 * Using non-symbolic operators rattles cages, and probably more
 significantly than new symbolic ones, and has been rejected in the past
 (`is`/`isnt`).

 So that's in the mix.

 # Using symbolic operators:

 ## Form

 The closest I can come to consistency with `==`/`===` and `!=`/`!==` is:

 LooseStrict
  ==   ===
  !=   !==
  <<=<
  >>=>
  <=   <==
  >=   >==

 We can think of the `=` in the middle as being 

Re: Re: Strict Relational Operators

[Darien Valentine]

> Personally I think `a < b` should just become a compile error if the
types are not number.

Breaking stuff aside, I think this is an important point. The fact that the
LT/GT operators do work on strings is a source of bugs. As with default
sort, I’ve seen code written a number of times where it was evident the
author expected the behavior would be more like
`Intl.Collator.prototype.compare`.

Unless I’m missing some important common use case for comparing strings
based on byte values (`assert('a' > 'B')`), I think `Number.gt`,
`Number.gte`, `Number.lt`, `Number.lte` would be a good solution.

On Wed, Apr 12, 2017 at 5:09 AM, T.J. Crowder <
tj.crow...@farsightsoftware.com> wrote:

> > Personally I think `a < b` should just become a compile error if the
> types are not number. TypeScript?
>
> I'm not following you. JavaScript variables don't have types, so it can't
> become a compile-time error; and making it one would *massively* break the
> web. (Yes, you can use TypeScript to get types if you like, but we're not
> talking about TypeScript.)
>
> > ...that's a separable concern which should not be part of the operator's
> behaviour IMO...
>
> There's no talk of changing how `<` and `>` (or `<=` and `>=`) work.
>
> But just as we have `==` (loose, coercing) and `===` (strict,
> non-coercing), the discussion is about having strict non-coercing versions
> of `<`, `>`, `<=`, and `>=`.
>
> -- T.J. Crowder
>
>
> On Wed, Apr 12, 2017 at 10:00 AM, Alexander Jones  wrote:
>
>> Personally I think `a < b` should just become a compile error if the
>> types are not number. TypeScript?
>>
>> If you want to also check that they are both number (that's surely what
>> we mean here and not that they are both string!) and return `false` if not,
>> that's a separable concern which should not be part of the operator's
>> behaviour IMO. It would appear to just mask fundamental typing errors,
>> unless I am missing some perspective?
>>
>> Alex
>>
>> On Wed, 12 Apr 2017 at 09:02, T.J. Crowder > om> wrote:
>>
>>> Grr, there's always something. I forgot to mention that solving this
>>> with functions is an option because short-circuiting isn't an issue, both
>>> operands have to be evaluated by these relational operators anyway. So
>>> unlike the motiviations for infix functions or macros or whatever, we don't
>>> have that issue here.
>>>
>>> -- T.J. Crowder
>>>
>>>
>>> On Wed, Apr 12, 2017 at 8:56 AM, T.J. Crowder <
>>> tj.crow...@farsightsoftware.com> wrote:
>>>
>>> Very interesting stuff so far.
>>>
>>> My take on some options, organized into sections:
>>>
>>> * Solving it in userland
>>> * Using symbolic operators
>>> * Using functions
>>> * Using non-symbolic operators
>>>
>>> # Solving it in userland:
>>>
>>> Anyone wanting strict relational operators today can readily give
>>> themselves functions for it:
>>>
>>> ```js
>>> const lt = (a, b) => typeof a === typeof b && a < b;
>>> ```
>>>
>>> Usage:
>>>
>>> ```js
>>> if (lt(a, b)) {
>>> // ...
>>> }
>>> ```
>>>
>>> So the question is whether the value of having a standard way of
>>> expressing this is worth the cost of adding it?
>>>
>>> Playing into that is that various options come with varying costs:
>>>
>>> * Using symbolic operators has a cost, but doesn't change fundamentals;
>>> I'm not an implementer, but I'd think the cost would be fairly low (but
>>> non-zero). *Any* syntax change rattles parsing cages everywhere, but syntax
>>> changes are now fairly regular occurrences in JavaScript.
>>> * Using functions means no new syntax, which means not rattling parsing
>>> cages, and are polyfillable.
>>> * Using non-symbolic operators rattles cages, and probably more
>>> significantly than new symbolic ones, and has been rejected in the past
>>> (`is`/`isnt`).
>>>
>>> So that's in the mix.
>>>
>>> # Using symbolic operators:
>>>
>>> ## Form
>>>
>>> The closest I can come to consistency with `==`/`===` and `!=`/`!==` is:
>>>
>>> LooseStrict
>>>  ==   ===
>>>  !=   !==
>>>  <<=<
>>>  >>=>
>>>  <=   <==
>>>  >=   >==
>>>
>>> We can think of the `=` in the middle as being what signifies the strict
>>> type aspect. The second `<` and `>` on `<=<` and `>=>` are a hack, but a
>>> reasonable hack that's in the spirit of the original two strict operators.
>>> :-)
>>>
>>> ## Semantics
>>>
>>> Because they're like `!==` and `===`, their semantics would have to be
>>> in line with `!==` and `===`: The result is `true` if the operands are of
>>> the same type and the relation is true, `false` otherwise.
>>>
>>> # Using functions:
>>>
>>> ## Form
>>>
>>> Given `Object.is(value1, value2)` there's an argument for putting these
>>> on `Object` as well. But `Object` is an odd place for them (and indeed for
>>> `is`). Perhaps we need a place for these to go. But sticking with `Object`
>>> for now:
>>>
>>> ```js
>>> Object.lt(value1, value2)
>>> Object.gt(value1, value2)
>>> 

Re: Re: Strict Relational Operators

[T.J. Crowder]

> Personally I think `a < b` should just become a compile error if the
types are not number. TypeScript?

I'm not following you. JavaScript variables don't have types, so it can't
become a compile-time error; and making it one would *massively* break the
web. (Yes, you can use TypeScript to get types if you like, but we're not
talking about TypeScript.)

> ...that's a separable concern which should not be part of the operator's
behaviour IMO...

There's no talk of changing how `<` and `>` (or `<=` and `>=`) work.

But just as we have `==` (loose, coercing) and `===` (strict,
non-coercing), the discussion is about having strict non-coercing versions
of `<`, `>`, `<=`, and `>=`.

-- T.J. Crowder


On Wed, Apr 12, 2017 at 10:00 AM, Alexander Jones  wrote:

> Personally I think `a < b` should just become a compile error if the types
> are not number. TypeScript?
>
> If you want to also check that they are both number (that's surely what we
> mean here and not that they are both string!) and return `false` if not,
> that's a separable concern which should not be part of the operator's
> behaviour IMO. It would appear to just mask fundamental typing errors,
> unless I am missing some perspective?
>
> Alex
>
> On Wed, 12 Apr 2017 at 09:02, T.J. Crowder  com> wrote:
>
>> Grr, there's always something. I forgot to mention that solving this with
>> functions is an option because short-circuiting isn't an issue, both
>> operands have to be evaluated by these relational operators anyway. So
>> unlike the motiviations for infix functions or macros or whatever, we don't
>> have that issue here.
>>
>> -- T.J. Crowder
>>
>>
>> On Wed, Apr 12, 2017 at 8:56 AM, T.J. Crowder <
>> tj.crow...@farsightsoftware.com> wrote:
>>
>> Very interesting stuff so far.
>>
>> My take on some options, organized into sections:
>>
>> * Solving it in userland
>> * Using symbolic operators
>> * Using functions
>> * Using non-symbolic operators
>>
>> # Solving it in userland:
>>
>> Anyone wanting strict relational operators today can readily give
>> themselves functions for it:
>>
>> ```js
>> const lt = (a, b) => typeof a === typeof b && a < b;
>> ```
>>
>> Usage:
>>
>> ```js
>> if (lt(a, b)) {
>> // ...
>> }
>> ```
>>
>> So the question is whether the value of having a standard way of
>> expressing this is worth the cost of adding it?
>>
>> Playing into that is that various options come with varying costs:
>>
>> * Using symbolic operators has a cost, but doesn't change fundamentals;
>> I'm not an implementer, but I'd think the cost would be fairly low (but
>> non-zero). *Any* syntax change rattles parsing cages everywhere, but syntax
>> changes are now fairly regular occurrences in JavaScript.
>> * Using functions means no new syntax, which means not rattling parsing
>> cages, and are polyfillable.
>> * Using non-symbolic operators rattles cages, and probably more
>> significantly than new symbolic ones, and has been rejected in the past
>> (`is`/`isnt`).
>>
>> So that's in the mix.
>>
>> # Using symbolic operators:
>>
>> ## Form
>>
>> The closest I can come to consistency with `==`/`===` and `!=`/`!==` is:
>>
>> LooseStrict
>>  ==   ===
>>  !=   !==
>>  <<=<
>>  >>=>
>>  <=   <==
>>  >=   >==
>>
>> We can think of the `=` in the middle as being what signifies the strict
>> type aspect. The second `<` and `>` on `<=<` and `>=>` are a hack, but a
>> reasonable hack that's in the spirit of the original two strict operators.
>> :-)
>>
>> ## Semantics
>>
>> Because they're like `!==` and `===`, their semantics would have to be in
>> line with `!==` and `===`: The result is `true` if the operands are of the
>> same type and the relation is true, `false` otherwise.
>>
>> # Using functions:
>>
>> ## Form
>>
>> Given `Object.is(value1, value2)` there's an argument for putting these
>> on `Object` as well. But `Object` is an odd place for them (and indeed for
>> `is`). Perhaps we need a place for these to go. But sticking with `Object`
>> for now:
>>
>> ```js
>> Object.lt(value1, value2)
>> Object.gt(value1, value2)
>> Object.lte(value1, value2)
>> Object.gte(value1, value2)
>> ```
>>
>> So:
>>
>> ```js
>> if (Object.lt(a, b)) {
>> // ...
>> }
>> ```
>>
>> Verbose, and again, using `Object` if I'm comparing numbers or strings
>> seems wrong. But it's consistent with the prior practice of `Object.is`.
>>
>> Michael J. Ryan suggested putting them on `Number`, `String`, and
>> `Object` instead, on the theory that if you're being strict, you know what
>> you're comparing. I'm not sure I agree that you do (a generic "take the
>> lower of these two" function, for instance), but there's something there.
>> It doesn't address the verbosity issue. (Presumably we only need `Number`
>> and `String` though, unless we're going to introduce a whole mechanism for
>> relational comparison of objects. Or unless the `Object` version just hands
>> off to 

Re: Re: Strict Relational Operators

[Alexander Jones]

Personally I think `a < b` should just become a compile error if the types
are not number. TypeScript?

If you want to also check that they are both number (that's surely what we
mean here and not that they are both string!) and return `false` if not,
that's a separable concern which should not be part of the operator's
behaviour IMO. It would appear to just mask fundamental typing errors,
unless I am missing some perspective?

Alex

On Wed, 12 Apr 2017 at 09:02, T.J. Crowder 
wrote:

> Grr, there's always something. I forgot to mention that solving this with
> functions is an option because short-circuiting isn't an issue, both
> operands have to be evaluated by these relational operators anyway. So
> unlike the motiviations for infix functions or macros or whatever, we don't
> have that issue here.
>
> -- T.J. Crowder
>
>
> On Wed, Apr 12, 2017 at 8:56 AM, T.J. Crowder <
> tj.crow...@farsightsoftware.com> wrote:
>
> Very interesting stuff so far.
>
> My take on some options, organized into sections:
>
> * Solving it in userland
> * Using symbolic operators
> * Using functions
> * Using non-symbolic operators
>
> # Solving it in userland:
>
> Anyone wanting strict relational operators today can readily give
> themselves functions for it:
>
> ```js
> const lt = (a, b) => typeof a === typeof b && a < b;
> ```
>
> Usage:
>
> ```js
> if (lt(a, b)) {
> // ...
> }
> ```
>
> So the question is whether the value of having a standard way of
> expressing this is worth the cost of adding it?
>
> Playing into that is that various options come with varying costs:
>
> * Using symbolic operators has a cost, but doesn't change fundamentals;
> I'm not an implementer, but I'd think the cost would be fairly low (but
> non-zero). *Any* syntax change rattles parsing cages everywhere, but syntax
> changes are now fairly regular occurrences in JavaScript.
> * Using functions means no new syntax, which means not rattling parsing
> cages, and are polyfillable.
> * Using non-symbolic operators rattles cages, and probably more
> significantly than new symbolic ones, and has been rejected in the past
> (`is`/`isnt`).
>
> So that's in the mix.
>
> # Using symbolic operators:
>
> ## Form
>
> The closest I can come to consistency with `==`/`===` and `!=`/`!==` is:
>
> LooseStrict
>  ==   ===
>  !=   !==
>  <<=<
>  >>=>
>  <=   <==
>  >=   >==
>
> We can think of the `=` in the middle as being what signifies the strict
> type aspect. The second `<` and `>` on `<=<` and `>=>` are a hack, but a
> reasonable hack that's in the spirit of the original two strict operators.
> :-)
>
> ## Semantics
>
> Because they're like `!==` and `===`, their semantics would have to be in
> line with `!==` and `===`: The result is `true` if the operands are of the
> same type and the relation is true, `false` otherwise.
>
> # Using functions:
>
> ## Form
>
> Given `Object.is(value1, value2)` there's an argument for putting these on
> `Object` as well. But `Object` is an odd place for them (and indeed for
> `is`). Perhaps we need a place for these to go. But sticking with `Object`
> for now:
>
> ```js
> Object.lt(value1, value2)
> Object.gt(value1, value2)
> Object.lte(value1, value2)
> Object.gte(value1, value2)
> ```
>
> So:
>
> ```js
> if (Object.lt(a, b)) {
> // ...
> }
> ```
>
> Verbose, and again, using `Object` if I'm comparing numbers or strings
> seems wrong. But it's consistent with the prior practice of `Object.is`.
>
> Michael J. Ryan suggested putting them on `Number`, `String`, and `Object`
> instead, on the theory that if you're being strict, you know what you're
> comparing. I'm not sure I agree that you do (a generic "take the lower of
> these two" function, for instance), but there's something there. It doesn't
> address the verbosity issue. (Presumably we only need `Number` and `String`
> though, unless we're going to introduce a whole mechanism for relational
> comparison of objects. Or unless the `Object` version just hands off to the
> `Number` or `String` version based on the first operand type.)
>
> ## Semantics
>
> Using functions gives us the opportunity to use slightly different
> semantics:
>
> 1. `true`: The operands are the same type and the relation is true
> 2. `false`: The operands are the same type and the relation is false
> 3. `undefined`: The operands are of different types
>
> This takes advantage of the fact `undefined` is falsy to not get in the
> way of people just using the result in a condition, but if they examine the
> result itself, it's possible to differentiate between #2 and #3.
>
> Sadly, `Object.is` (the exposed version of the SameValue algorithm) does
> not make this distinction.
>
> # Non-symbolic operators
>
> JavaScript already has at least one binary operator that isn't symbolic:
> `in`. Maybe there's a case for adding more. Brendan Eich is [on record](
> 

Re: Re: Strict Relational Operators

[T.J. Crowder]

Grr, there's always something. I forgot to mention that solving this with
functions is an option because short-circuiting isn't an issue, both
operands have to be evaluated by these relational operators anyway. So
unlike the motiviations for infix functions or macros or whatever, we don't
have that issue here.

-- T.J. Crowder

On Wed, Apr 12, 2017 at 8:56 AM, T.J. Crowder <
tj.crow...@farsightsoftware.com> wrote:

> Very interesting stuff so far.
>
> My take on some options, organized into sections:
>
> * Solving it in userland
> * Using symbolic operators
> * Using functions
> * Using non-symbolic operators
>
> # Solving it in userland:
>
> Anyone wanting strict relational operators today can readily give
> themselves functions for it:
>
> ```js
> const lt = (a, b) => typeof a === typeof b && a < b;
> ```
>
> Usage:
>
> ```js
> if (lt(a, b)) {
> // ...
> }
> ```
>
> So the question is whether the value of having a standard way of
> expressing this is worth the cost of adding it?
>
> Playing into that is that various options come with varying costs:
>
> * Using symbolic operators has a cost, but doesn't change fundamentals;
> I'm not an implementer, but I'd think the cost would be fairly low (but
> non-zero). *Any* syntax change rattles parsing cages everywhere, but syntax
> changes are now fairly regular occurrences in JavaScript.
> * Using functions means no new syntax, which means not rattling parsing
> cages, and are polyfillable.
> * Using non-symbolic operators rattles cages, and probably more
> significantly than new symbolic ones, and has been rejected in the past
> (`is`/`isnt`).
>
> So that's in the mix.
>
> # Using symbolic operators:
>
> ## Form
>
> The closest I can come to consistency with `==`/`===` and `!=`/`!==` is:
>
> LooseStrict
>  ==   ===
>  !=   !==
>  <<=<
>  >>=>
>  <=   <==
>  >=   >==
>
> We can think of the `=` in the middle as being what signifies the strict
> type aspect. The second `<` and `>` on `<=<` and `>=>` are a hack, but a
> reasonable hack that's in the spirit of the original two strict operators.
> :-)
>
> ## Semantics
>
> Because they're like `!==` and `===`, their semantics would have to be in
> line with `!==` and `===`: The result is `true` if the operands are of the
> same type and the relation is true, `false` otherwise.
>
> # Using functions:
>
> ## Form
>
> Given `Object.is(value1, value2)` there's an argument for putting these on
> `Object` as well. But `Object` is an odd place for them (and indeed for
> `is`). Perhaps we need a place for these to go. But sticking with `Object`
> for now:
>
> ```js
> Object.lt(value1, value2)
> Object.gt(value1, value2)
> Object.lte(value1, value2)
> Object.gte(value1, value2)
> ```
>
> So:
>
> ```js
> if (Object.lt(a, b)) {
> // ...
> }
> ```
>
> Verbose, and again, using `Object` if I'm comparing numbers or strings
> seems wrong. But it's consistent with the prior practice of `Object.is`.
>
> Michael J. Ryan suggested putting them on `Number`, `String`, and `Object`
> instead, on the theory that if you're being strict, you know what you're
> comparing. I'm not sure I agree that you do (a generic "take the lower of
> these two" function, for instance), but there's something there. It doesn't
> address the verbosity issue. (Presumably we only need `Number` and `String`
> though, unless we're going to introduce a whole mechanism for relational
> comparison of objects. Or unless the `Object` version just hands off to the
> `Number` or `String` version based on the first operand type.)
>
> ## Semantics
>
> Using functions gives us the opportunity to use slightly different
> semantics:
>
> 1. `true`: The operands are the same type and the relation is true
> 2. `false`: The operands are the same type and the relation is false
> 3. `undefined`: The operands are of different types
>
> This takes advantage of the fact `undefined` is falsy to not get in the
> way of people just using the result in a condition, but if they examine the
> result itself, it's possible to differentiate between #2 and #3.
>
> Sadly, `Object.is` (the exposed version of the SameValue algorithm) does
> not make this distinction.
>
> # Non-symbolic operators
>
> JavaScript already has at least one binary operator that isn't symbolic:
> `in`. Maybe there's a case for adding more. Brendan Eich is [on record](
> https://esdiscuss.org/topic/suggestion-mapping-
> symbolic-infix-ops-to-binary-functions#content-5) five years ago as
> having issues with them:
>
> > > modulo, div, divmod, has, extends
>
> > These are much better as methods. Polyfillable, but also not subject to
> weird line terminator restrictions on the left. Same arguments killed
> is/isnt.
>
> Hence `Object.is`, presumably (the linked discussion was about infix
> functions, not `is`). I don't know if that view has shifted in the
> subsequent five years; there have been big changes in the way JavaScript
> moves forward. But 

Re: Re: Strict Relational Operators

[T.J. Crowder]

Very interesting stuff so far.

My take on some options, organized into sections:

* Solving it in userland
* Using symbolic operators
* Using functions
* Using non-symbolic operators

# Solving it in userland:

Anyone wanting strict relational operators today can readily give
themselves functions for it:

```js
const lt = (a, b) => typeof a === typeof b && a < b;
```

Usage:

```js
if (lt(a, b)) {
// ...
}
```

So the question is whether the value of having a standard way of expressing
this is worth the cost of adding it?

Playing into that is that various options come with varying costs:

* Using symbolic operators has a cost, but doesn't change fundamentals; I'm
not an implementer, but I'd think the cost would be fairly low (but
non-zero). *Any* syntax change rattles parsing cages everywhere, but syntax
changes are now fairly regular occurrences in JavaScript.
* Using functions means no new syntax, which means not rattling parsing
cages, and are polyfillable.
* Using non-symbolic operators rattles cages, and probably more
significantly than new symbolic ones, and has been rejected in the past
(`is`/`isnt`).

So that's in the mix.

# Using symbolic operators:

## Form

The closest I can come to consistency with `==`/`===` and `!=`/`!==` is:

LooseStrict
 ==   ===
 !=   !==
 <<=<
 >>=>
 <=   <==
 >=   >==

We can think of the `=` in the middle as being what signifies the strict
type aspect. The second `<` and `>` on `<=<` and `>=>` are a hack, but a
reasonable hack that's in the spirit of the original two strict operators.
:-)

## Semantics

Because they're like `!==` and `===`, their semantics would have to be in
line with `!==` and `===`: The result is `true` if the operands are of the
same type and the relation is true, `false` otherwise.

# Using functions:

## Form

Given `Object.is(value1, value2)` there's an argument for putting these on
`Object` as well. But `Object` is an odd place for them (and indeed for
`is`). Perhaps we need a place for these to go. But sticking with `Object`
for now:

```js
Object.lt(value1, value2)
Object.gt(value1, value2)
Object.lte(value1, value2)
Object.gte(value1, value2)
```

So:

```js
if (Object.lt(a, b)) {
// ...
}
```

Verbose, and again, using `Object` if I'm comparing numbers or strings
seems wrong. But it's consistent with the prior practice of `Object.is`.

Michael J. Ryan suggested putting them on `Number`, `String`, and `Object`
instead, on the theory that if you're being strict, you know what you're
comparing. I'm not sure I agree that you do (a generic "take the lower of
these two" function, for instance), but there's something there. It doesn't
address the verbosity issue. (Presumably we only need `Number` and `String`
though, unless we're going to introduce a whole mechanism for relational
comparison of objects. Or unless the `Object` version just hands off to the
`Number` or `String` version based on the first operand type.)

## Semantics

Using functions gives us the opportunity to use slightly different
semantics:

1. `true`: The operands are the same type and the relation is true
2. `false`: The operands are the same type and the relation is false
3. `undefined`: The operands are of different types

This takes advantage of the fact `undefined` is falsy to not get in the way
of people just using the result in a condition, but if they examine the
result itself, it's possible to differentiate between #2 and #3.

Sadly, `Object.is` (the exposed version of the SameValue algorithm) does
not make this distinction.

# Non-symbolic operators

JavaScript already has at least one binary operator that isn't symbolic:
`in`. Maybe there's a case for adding more. Brendan Eich is [on record](
https://esdiscuss.org/topic/suggestion-mapping-symbolic-infix-ops-to-binary-functions#content-5)
five years ago as having issues with them:

> > modulo, div, divmod, has, extends

> These are much better as methods. Polyfillable, but also not subject to
weird line terminator restrictions on the left. Same arguments killed
is/isnt.

Hence `Object.is`, presumably (the linked discussion was about infix
functions, not `is`). I don't know if that view has shifted in the
subsequent five years; there have been big changes in the way JavaScript
moves forward. But that was an objection at least then.

## Form

`lt`, `lte`, `gt`, and `gte`. And while we're at it, `eq` and `noteq`. So:

```js
if (a lt b) {
// ...
}
```

To avoid breaking the web, the new non-symbolic operators would have to
remain valid identifiers, only being operators by context, a bit like how
`for` can be a literal property name (`obj.for`) as of ES5 because we know
from context that it's not the `for` statement. But I assume (not being a
parser guy) that it's more complex to handle the above (those "weird line
terminator conditions on the left" Eich mentioned).

## Semantics

Like functions, non-symbolic operators let us consider slightly 

Re: Re: throwif operator

[Нурбек]

Yes, throw expressions would be helpful to shorten if statements to
one-liner ternary operators. I agree with you.
___
es-discuss mailing list
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https://mail.mozilla.org/listinfo/es-discuss

Re: Re: Strict Relational Operators

[Michael J. Ryan]

Thinking on it... (Number|Object|String) .strict(Equal|Greater|Less...)
Methods (a, b) might be better...  If either value isn't a match for the
bound type, it's a false, even if both sides are equal...

Ex,.

Number.strictEqual(null, null)  false

Object.strictEqual(1, 1)  false
...

If you're doing a strict compare, one can presume you should know what
you're comparing.


-- 
Michael J. Ryan - track...@gmail.com - http://tracker1.info

Please excuse grammar errors and typos, as this message was sent from my
phone.

On Apr 11, 2017 10:46 PM, "felix"  wrote:

> Maybe every operator can have a non-coercing variant?
>
> One possible syntax is to have a modifier on operators
> x = a (<) b (+) c (&&) (!)d;
> if (x (!=) y) ...
>
> Another possible syntax is to have a modifier on expressions
> x = #(a < b + c && !d)
> if #(x != y) ...
>
> On Tue, Apr 11, 2017 at 7:48 PM, Darien Valentine 
> wrote:
> > Although I’m unsure if this is wise given there are already eleven
> symbols
> > that are combinations of `=` and `<`/`>`, for symmetry with `==` and
> `===`
> > I’d imagine something like this:
> >
> > ```
> > COERCIVE  STRICT
> >> =>=
> > < =<=
> >>==>==
> > <==<==
> > ```
> >
> > Could also follow the pattern `>==` (strict GT) and `<===` (strict GTE),
> > which avoids the awkwardness of the latter two sharing opening chars with
> > `=>`, but that seems more ambiguous since `>==` doesn’t let you infer
> > whether it means strict GT or strict GTE.
> >
> > It’d be nice to have this functionality built in, but I wonder if it’d
> > possibly be preferable to provide it through methods of one of the
> built-in
> > objects, rather than as operators. Functions after all are more flexible.
> >
> > ___
> > 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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