On 17.11.2011 11:41, David Herman wrote:
On Nov 16, 2011, at 11:27 PM, Mark S. Miller wrote:
On Wed, Nov 16, 2011 at 11:24 PM, David Herman <[email protected]
<mailto:[email protected]>> wrote:
obj with { foo: 12 } with { bar: 13 } with { baz: 17 }
I don't get it yet. What do you mean by "dynamically extending
prototype chains"? What does the above expression do and evaluate to?
My first answer was glib, sorry. I'm proposing `with' as a replacement
syntax for <|. So the above expression evaluates to the same as
obj <| { foo: 12 } <| { bar: 13 } <| { baz: 17 }
which in turn, if I've got this right, would be equivalent to
Object.create(Object.create(Object.create(obj, { foo: { value: 12,
enumerable: true,
configurable: true,
writable:
true } }),
{ bar: { value: 13,
enumerable: true,
configurable: true,
writable: true } }),
{ baz: { value: 17,
enumerable: true,
configurable: true,
writable: true } })
since in this example I only used the object literal variant. (The
function, array, etc variants do things that Object.create can't do.)
Once again, it's absolutely the same approach which I showed yesterday
with using `extends'
(https://mail.mozilla.org/pipermail/es-discuss/2011-November/018478.html).
In order to avoid confusion with `with', which had old and used for
years semantics, I still propose to use `extends' instead.
Is it just great that we have the _same inheritance model_ as for simple
objects as well as for classes?
// object inherits
var foo extends bar {
x: 100
}
// class inherits
class Foo extends Bar {
constructor (x, y, z) { ... }
}
P.S.: Scala e.g. uses a similar approach. But they use `object' keyword
when inheriting from objects:
object foo extends bar {
...
}
Though, they also may use `with' in this context:
object foo extends bar with baz {
...
}
thus baz is a mixin. The same with classes:
class Foo extends Bar with baz {
....
}
Dmitry.
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