domenic at domenicdenicola.com (2013-08-02T20:39:42.112Z)
On Tue, Jul 30, 2013 at 9:19 PM, Brendan Eich <brendan at mozilla.com> wrote: > Lots of ways, e.g., `this` in bound methods, Only useful for instance-private instance variables, in which case you may as well use lexically captured per-instance state. > `this` after suitable instanceof tests with no mutable [[Prototype]] > (e.g., A and B are sealed, manually in ES6 alas, but still doable). Doesn't resist theft by proxy, since one can easily construct a proxy that passes that instanceof test.
On Tue, Jul 30, 2013 at 9:19 PM, Brendan Eich <brendan at mozilla.com> wrote: > Mark Miller wrote: > > On Tue, Jul 30, 2013 at 8:36 PM, Brendan Eich <brendan at mozilla.com<mailto: >> brendan at mozilla.com>> wrote: >> >> Mark S. Miller wrote: >> >> Aside from this confinement issue, all other the advantages >> that unique symbols have over unique-ish strings seem minor to >> me. The biggest is default non-enumerability, when we're >> getting away (admittedly slowly) from enumerability being >> significant anyway. IMO, if the only advantages of unique >> symbols over unique-ish strings are these minor ones, then >> they don't pull their weight. >> >> However, I don't understand the confinement scenario you have >> in mind. Can you give an example? >> >> >> A friend field a la C++ "friend", e.g.: >> >> module ... { >> const friend = Symbol(); // however it's spelled >> class A { ... } >> class B { ... } >> } >> >> where fiend is used in the ... elisions but only to access >> properties of objects known to be instanceof A or B. >> >> >> Known how? >> > > Lots of ways, e.g., |this| in bound methods, Only useful for instance-private instance variables, in which case you may as well use lexically captured per-instance state. > |this| after suitable instanceof tests with no mutable [[Prototype]] > (e.g., A and B are sealed, manually in ES6 alas, but still doable). Doesn't resist theft by proxy, since one can easily construct a proxy that passes that instanceof test. > > > /be > -- Cheers, --MarkM -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20130730/6593f9c6/attachment-0001.html>