On Aug 28, 2008, at 10:36 AM, Yuh-Ruey Chen wrote: > I've taken a look at that, and while it does address free > variables, I'd > still rather not have to sprinkle redundant |var|s everywhere.
Those vars are helpful to some readers, who otherwise have to learn the Python/Ruby/TCL model and look for prior nonlocals. Programmers repeat var in unrelated paragraphs precisely to help the "spot reader" (including themselves, when rearranging code as Ingvar pointed out). I'm not criticizing the opt-out local scoping approach. Indeed, Bill Joy tried too late in 1995 to get me to switch JS to use it, without a pragma -- just an incompatible change. At that point there was already too much content depending on it (Marc Andreessen made the same point about Mosaic and NCSA httpd already having "too many" -- 80 or so -- sites, hosting quirky HTML that motivated error- corrections in the Mosaic parser). Between the utility of var for some readers and writers today, and the closer concept of pure lexical scope that Dave proposes, there is less distance than there is between today's JS and an opt-out local scoping regime. This distance argument is important both for the language spec, to conserve concepts, and for programmers who have to read and write code reused (read and extended) by other programmers. Adding an opt- out local scoping mechanism that sees wide adoption would split the world of JS programs in two. I don't think it would take over completely, ever, so it would leave a gulf between the compatible scoping model and the opt-out local scoping model. Again I'm not bike-shedding the details of your proposal or knocking the virtue of opt-out local scoping in other languages. I'm pointing out that we can't go back to 1995 and change JS to have a single better scoping system. Given the need for a pragmatic way to change the scoping model, resulting in *two* models in practice if the new way sees adoption, I am in favor of a shorter-distance proposal that does less violence to the habits of JS hackers. Beyond this point, lexical scope actually reforms the global object by getting it out of the scope chain. And it allows global bindings that people want to count on (Date, alert, document) to become lexical, possibly even immutable depending on how we do it. /be _______________________________________________ Es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
