The fact is that "dynamic scope" is used to mean multiple things: 1) the "stack-like" semantics employed by e.g. the original Lisps, and 2) any non-static scoping semantics. The former was so famous that it came to be the common usage of the term, but #1 is really just a special case of #2. I've seen people use it both ways. Sam's using it the second way, Dmitry is using it the first way (and trying to claim that Sam's way is wrong). It's not really a deep issue, just ambiguous terminology.
Dave On Apr 15, 2011, at 2:31 PM, Brendan Eich wrote: > I've noticed that there are at least two uses of dynamic scope, all > maledictions (and so tending to blur together into one general curse): > > * Using the dynamic link or call stack as scope chain link (clearly evil; er, > eval ;-). > > * Having a scope chain element be a mutable object in which bindings can come > and even go (also bad, and the issue here in ES5 non-strict and older JS). > > We could try to call the latter "dynamic binding", but "binding" is so > horribly overused and overloaded informally... > > Not sure this helps :-(. > > /be > > On Apr 15, 2011, at 10:59 PM, Sam Tobin-Hochstadt wrote: > >> On Fri, Apr 15, 2011 at 4:53 PM, Mark S. Miller <[email protected]> wrote: >>>> >>>> I understand how dynamic scope works. And ES5 with the mutable global >>>> object has it: >>>> >>>> function bar() { return foo }; >>>> bar() // error: foo is not defined >>>> var foo = 7; >>>> bar(); // produces 7 >>>> >>>> Lexical scope would produce the error both times. >>> >>> Hi Sam, this does establish that ES5 does not have lexical scope. But I >>> don't how ES5 has dynamic scope. In the above example, the 'foo' that bar >>> has in scope during the second call still has nothing to do with what's in >>> scope at the call site from which bar is called. >> >> I think what you're saying is that if I then do: >> >> (function (){ var foo = 8; return bar(); })(); >> >> I'll get 7, not 8, which is certainly true. We can think of this as >> dynamically scoped with respect to "top-level" variables, ie those >> bound at the top level or unbound at the time of definition, or we can >> think of this as a variety of scoping that is neither lexical nor >> dynamic -- that's just a terminology question. >> -- >> sam th >> [email protected] > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
