David Herman wrote:
On Jun 15, 2012, at 5:57 PM, satyr wrote:
On Sat, Jun 16, 2012 at 4:33 AM, David Herman <[email protected]
<mailto:[email protected]>> 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
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