Re: ||= is much needed?
On Jun 15, 2012, at 5:57 PM, satyr wrote: On Sat, Jun 16, 2012 at 4:33 AM, David Herman dher...@mozilla.com wrote: As for null, I can see how there's confusion about whether to use null vs undefined, and so I can see why CoffeeScript would just try to blur the distinction between them. Not just for blurring. Rejecting `null` is essential for CoffeeScript's existence due to `?.`, the soak/safe access operator. I think you could make a case for ?. defaulting for both but ?? defaulting only undefined. The case goes something like this: - The purpose of ?? is to provide a default value when no value was provided. The way to say no value in JavaScript is undefined. - The purpose of ?. is to fail soft when doing a property lookup. Both null and undefined throw when doing a property lookup. Dave ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: ||= is much needed?
David Herman wrote: On Jun 15, 2012, at 5:57 PM, satyr wrote: On Sat, Jun 16, 2012 at 4:33 AM, David Herman dher...@mozilla.com mailto:dher...@mozilla.com wrote: As for null, I can see how there's confusion about whether to use null vs undefined, and so I can see why CoffeeScript would just try to blur the distinction between them. Not just for blurring. Rejecting `null` is essential for CoffeeScript's existence due to `?.`, the soak/safe access operator. I think you could make a case for ?. defaulting for both but ?? defaulting only undefined. The case goes something like this: - The purpose of ?? is to provide a default value when no value was provided. The way to say no value in JavaScript is undefined. - The purpose of ?. is to fail soft when doing a property lookup. Both null and undefined throw when doing a property lookup. Agreed. This is one choice, it's plausible because of the distinction between defaulting (which requires intentional passing of a please default sentinel value, or not passing a trailing actual argument) and soaking up null-or-undefined. Yes, we could make ?? and ??= do the same for null as for undefined. I'm not sure that's the right choice, but it's a choice. For foo.bar?.baz, though, the clearer choice is to avoid throwing, which means evaluating to undefined if foo.bar is missing (evaluates to undefined) *or* has a value not coercible to object type (null or undefined). See http://wiki.ecmascript.org/doku.php?id=strawman:existential_operator /be ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Existential operator (was: ||= is much needed?)
Sorry, meant to start a new thread for: http://wiki.ecmascript.org/doku.php?id=strawman:existential_operator As the Syntax section hints, we can't also adopt CoffeeScript's ?( variant, which enables foo.bar?(args, go, here).baz and the like. The C syntax heritage prevails. /be Brendan Eich wrote: David Herman wrote: On Jun 15, 2012, at 5:57 PM, satyr wrote: On Sat, Jun 16, 2012 at 4:33 AM, David Herman dher...@mozilla.com mailto:dher...@mozilla.com wrote: As for null, I can see how there's confusion about whether to use null vs undefined, and so I can see why CoffeeScript would just try to blur the distinction between them. Not just for blurring. Rejecting `null` is essential for CoffeeScript's existence due to `?.`, the soak/safe access operator. I think you could make a case for ?. defaulting for both but ?? defaulting only undefined. The case goes something like this: - The purpose of ?? is to provide a default value when no value was provided. The way to say no value in JavaScript is undefined. - The purpose of ?. is to fail soft when doing a property lookup. Both null and undefined throw when doing a property lookup. Agreed. This is one choice, it's plausible because of the distinction between defaulting (which requires intentional passing of a please default sentinel value, or not passing a trailing actual argument) and soaking up null-or-undefined. Yes, we could make ?? and ??= do the same for null as for undefined. I'm not sure that's the right choice, but it's a choice. For foo.bar?.baz, though, the clearer choice is to avoid throwing, which means evaluating to undefined if foo.bar is missing (evaluates to undefined) *or* has a value not coercible to object type (null or undefined). See http://wiki.ecmascript.org/doku.php?id=strawman:existential_operator /be ___ 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
