syntax for case ranges

Claude Pache claude.pache at gmail.com
Mon Feb 3 17:17:50 UTC 2020


Try typing `3 < 2 < 1` in the web console of your favourite browser, and see the result: it will evaluate to `true`. No, your browser isn’t buggy, it is just following blindly the semantics of `<`.

Modifying the meaning of `3 < 2 < 1` in order to make it evaluating  to `false` is a BC break. Is it acceptable? Dunno.

—Claude

> Le 3 févr. 2020 à 15:23, Naveen Chawla <naveen.chwl at gmail.com> a écrit :
> 
> Hi!
> 
> I didn't understand your reply.
> 
> I think currently it would raise an error, because 1 < 2 < 3 is currently saying (probably) true < 3.
> 
> But a "new" syntax could possibly parse that as a "chain" of comparisons.
> 
> Would this be acceptable to introduce into JavaScript (just curious)?
> 
> I've probably missed your point entirely, because I saw a short message "3 < 2 < 1 //true", and I've assumed you meant it in reverse.
> 
> On Sat, 1 Feb 2020 at 23:12, Mark S. Miller <erights at gmail.com <mailto:erights at gmail.com>> wrote:
> 3 < 2 < 1;  // true
> 
> 
> On Sat, Feb 1, 2020 at 3:03 AM Naveen Chawla <naveen.chwl at gmail.com <mailto:naveen.chwl at gmail.com>> wrote:
> Certain languages allow the expression 0<x<5. Does anybody know if this would be syntactically possible in JavaScript? Of course this would only apply for "if"/"while" statements.
> 
> On Fri, 31 Jan 2020 at 22:41, Isiah Meadows <contact at isiahmeadows.com <mailto:contact at isiahmeadows.com>> wrote:
> Still better to discuss it there - it's highly related to your suggestion. And I'm pretty sure an issue already exists related to that.
> 
> On Fri, Jan 31, 2020 at 09:06 Sultan <thysultan at gmail.com <mailto:thysultan at gmail.com>> wrote:
> The pattern matching proposal does not handles the mentioned case:
> 
> switch(type) { case 0...5: } being the equivalent of switch(type) { case 0: case 1: case 2: case 3: case 4: case 5: }
> 
> On Fri, Jan 31, 2020 at 7:36 PM Bruno Macabeus <bruno.macabeus at gmail.com <mailto:bruno.macabeus at gmail.com>> wrote:
> I agree with Oriol.
> We already have the proposal pattern matching, that has a very similar effect.
> I think that is better to improve pattern matching proposal in order to be able to match using ranges (or at least check if it's good to do) instead of create a new proposal.
> 
> On Fri, 31 Jan 2020 at 14:08, Oriol _ <oriol-bugzilla at hotmail.com <mailto:oriol-bugzilla at hotmail.com>> wrote:
> This sounds like https://github.com/tc39/proposal-pattern-matching <https://github.com/tc39/proposal-pattern-matching>
> 
> El 31/1/20 a les 10:57, Sultan ha escrit:
>> For example, the following:
>> 
>> switch (value) {
>>     case 0...9: break
>>     case 'a'...'z': break
>> }
>> 
>> 
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> -----
> 
> Isiah Meadows
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>   Cheers,
>   --MarkM
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