Le 19/06/2012 11:40, Hemanth H.M a écrit :
As there is no keyword as 'or' so far, does something like *x =
x.value or 5 *sound better?
I realize I gave examples with default values in case of error, but it
doesn't have to be the case. Specifically in
let greedy = try obj.hints.greedy
an "or" statement would be cumbersome since there is already 'undefined'
as implicit or-value.
But why not.
David
On Tue, Jun 19, 2012 at 3:00 PM, David Bruant <bruan...@gmail.com
<mailto:bruan...@gmail.com>> wrote:
What about a more generic operator that would be able to silently
absorb any error?
let greedy = obj.hints?.greedy;
would become:
let greedy = silent obj.hints.greedy;
The semantic would be exactly the same.
The syntax is up to debate. Specifically, it would be nice to be
able to silence a part of an expression.
What about a 'try' without a catch?
let greedy = try obj.hints.greedy
let greedy = try{ obj.hints.greedy } || 22;
This is currently forbidden (I think for 2 reasons, one being that
a try must be followed by a catch or finally and the other that
try/catch cannot be used as expressions)
This idea is partly inspired by typeof which silences
ReferenceErrors, which I see as a feature YMMV.
It is also intended to make programs potentially more robust more
easily. For instance, JSON.stringify can throw errors in the rare
case of cyclic references. But very few people know that. To make
a robust program using JSON.stringify, one would just need to turn:
let s = JSON.stringify(o)
into
let s = try{ JSON.stringify(o) } || DEFAULT_VALUE;
instead of the current:
let s;
try{
s = JSON.stringify(o)
}
catch(e){
// I don't care about the error anyway
s = DEFAULT_VALUE;
}
David
Le 18/06/2012 07:11, Brendan Eich a écrit :
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>
<mailto: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
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/-- Hemanth HM/
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