Re: Setting a property in the prototype chain?

On Apr 11, 2011, at 6:45 PM, Axel Rauschmayer wrote: >> var obj={}.valueOf.call(obj); // ToObject in case primitive value passed > > Can you explain how this works? > > - Why {} and not Object.prototype? > > - I know valueOf as a method that returns a primitive if an object can be > converte

Re: Setting a property in the prototype chain?

> var obj={}.valueOf.call(obj); // ToObject in case primitive value passed Can you explain how this works? - Why {} and not Object.prototype? - I know valueOf as a method that returns a primitive if an object can be converted to one and |this|, otherwise. Oddly enough, this works both in stric

Re: value proxies, fundamental traps for binary operators, precedence

On Apr 8, 2011, at 11:29 AM, Claus Reinke wrote: > I finally got a first look at the 'Virtual Values for Language Extension' > paper referred to in the value proxies strawman [1], > and suddenly find value proxies more interesting. > > Somehow the term proxy never suggested to me that this > wou

Re: 'this' is more complicated than I thought (PropertyReferences break equivalences)

On 4/11/11, Claus Reinke wrote: > Like most Javascript programmers, I have tended to follow > a simple rule for functions using 'this': eta-expand method > selections, use .bind, or get into trouble. > That is unnecessary, inefficient, and adds clutter. That most JavaScript programmers do that sa

Re: 'this' is more complicated than I thought (PropertyReferences break equivalences)

On 4/11/11, Claus Reinke wrote: > Like most Javascript programmers, I have tended to follow > a simple rule for functions using 'this': eta-expand method > selections, use .bind, or get into trouble. > That is unnecessary and inefficient. Instead, I use the following algorithm: For instance metho

Re: Dependency injection and modules?

Yes, that's the idea. Best, Dave On Apr 11, 2011, at 7:45 AM, Axel Rauschmayer wrote: > My understanding is limited, but here it goes: > > You load modules in ES.next as follows: >> module JSON = require('http://json.org/modules/json2.js'); > > > A custom module loader (loosely related to a J

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

Sure, I'll buy that. There's a qualitative difference in how uncooperatively your program is behaving if it mutates primordials to violate their usual contracts, as opposed to simply creating an object that overrides hasOwnProperty, which ought to be allowed. The word "theory" might be a little

Re: Setting a property in the prototype chain?

On Apr 11, 2011, at 9:21 PM, David Bruant wrote: > Actually I was wrong I think. With the introduction of proxies, ES > engines won't be able to trivially prevent pd allocation as they could > with regular objects just based on static analysis (since static > analysis will often fail at saying whe

Re: Setting a property in the prototype chain?

Le 11/04/2011 22:01, Brendan Eich a écrit : > On Apr 11, 2011, at 8:58 PM, David Bruant wrote: > >> Le 11/04/2011 21:47, Brendan Eich a écrit : >>> On Apr 11, 2011, at 6:36 PM, Allen Wirfs-Brock wrote: >>> Personally, I prefer Object.getOwnPropertyDescriptor as a property existence test

Re: Setting a property in the prototype chain?

On Apr 11, 2011, at 12:47 PM, Brendan Eich wrote: >> > > Then the only downside is the pd allocation. Any way to avoid that? > > /be Use a GC that supports cheap allocation/recovery of short-lived objects :-) It's probably premature optimization to worry about that one pd allocation without

Re: Setting a property in the prototype chain?

On Apr 11, 2011, at 8:58 PM, David Bruant wrote: > Le 11/04/2011 21:47, Brendan Eich a écrit : >> On Apr 11, 2011, at 6:36 PM, Allen Wirfs-Brock wrote: >> >>> Personally, I prefer Object.getOwnPropertyDescriptor as a property >>> existence test because it doesn't have the reflection the meta-cir

Re: Setting a property in the prototype chain?

Le 11/04/2011 21:47, Brendan Eich a écrit : > On Apr 11, 2011, at 6:36 PM, Allen Wirfs-Brock wrote: > >> Personally, I prefer Object.getOwnPropertyDescriptor as a property existence >> test because it doesn't have the reflection the meta-circularity concern. I >> would write Dave's original func

Re: Setting a property in the prototype chain?

On Apr 11, 2011, at 6:36 PM, Allen Wirfs-Brock wrote: > Personally, I prefer Object.getOwnPropertyDescriptor as a property existence > test because it doesn't have the reflection the meta-circularity concern. I > would write Dave's original function as: > > function getDefiningObject(obj, key

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

On 11.04.2011 22:37, Mark S. Miller wrote: On Sun, Apr 10, 2011 at 5:27 PM, Dmitry A. Soshnikov mailto:dmitry.soshni...@gmail.com>> wrote: As I see it, you address the "issue" of unstratified meta-programming (note, I take the "issue" in quotes, since there's no a single meaning wh

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

On Mon, Apr 11, 2011 at 2:48 PM, Mike Samuel wrote: > 2011/4/11 Mark S. Miller : > > > We would like a notion of correctness that allows us to reason in a > modular > > manner: A correct composition of individually correct components should > > yield a correct composite, where the correctness of

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

2011/4/11 Mark S. Miller : > We would like a notion of correctness that allows us to reason in a modular > manner: A correct composition of individually correct components should > yield a correct composite, where the correctness of the composition depends > only on the contracts of the components

Re: ECMAScript Object equivalence classes proposal

On Fri, Apr 8, 2011 at 13:24, Brendan Eich wrote: > On Apr 8, 2011, at 12:59 PM, David Bruant wrote: > >> I'll agree that as long as it's fast enough for real life uses, the >> actual big-O or multiplicative constants are of no interest. For >> instance, the current inheritance has a O(n) complexi

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

On Sun, Apr 10, 2011 at 5:27 PM, Dmitry A. Soshnikov < dmitry.soshni...@gmail.com> wrote: > > As I see it, you address the "issue" of unstratified meta-programming > (note, I take the "issue" in quotes, since there's no a single meaning > whether the unstratified meta-level is so bad). > > It depe

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

Le 10/04/2011 23:27, Dmitry A. Soshnikov a écrit : > On 11.04.2011 18:07, Mark S. Miller wrote: >> On Sun, Apr 10, 2011 at 11:21 PM, David Herman > > wrote: >> >> I wondered if someone was going to make this point. >> >> > That should be >> > >> >

Re: Setting a property in the prototype chain?

Personally, I prefer Object.getOwnPropertyDescriptor as a property existence test because it doesn't have the reflection the meta-circularity concern. I would write Dave's original function as: function getDefiningObject(obj, key) { var obj={}.valueOf.call(obj); // ToObject in case primiti

Re: When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

On 11.04.2011 18:07, Mark S. Miller wrote: On Sun, Apr 10, 2011 at 11:21 PM, David Herman > wrote: I wondered if someone was going to make this point. > That should be > > while (!{}.hasOwnProperty.call(obj, key)) > > which works even

Re: Dependency injection and modules?

My understanding is limited, but here it goes: You load modules in ES.next as follows: > module JSON = require('http://json.org/modules/json2.js'); A custom module loader (loosely related to a Java class loader) can be used to intercept the module loading and return a different module. That is,

Re: Dependency injection and modules?

Could you, or someone else, please explain what changing the semantics of module URLs means? DI is an important issue and I'd like to understand how it is intended to be achieved in the future module system. On Mon, Apr 11, 2011 at 8:52 AM, Axel Rauschmayer wrote: >>> I'm not sure how this would

When is a JavaScript program "correct"? (was: Setting a property in the prototype chain?)

On Sun, Apr 10, 2011 at 11:21 PM, David Herman wrote: > I wondered if someone was going to make this point. > > > That should be > > > > while (!{}.hasOwnProperty.call(obj, key)) > > > > which works even if obj has an own property named 'hasOwnProperty'. > > Not if someone mutates Object

Re: Dependency injection and modules?

>> I'm not sure how this would be done best or how useful it would be, but: has >> dependency injection been considered as a use case for modules (e.g. to swap >> modules during testing)? >> >> One possibility might be to give modules parameters that module clients have >> to provide. > The mo

Re: 'this' is more complicated than I thought (PropertyReferences break equivalences)

The behavior of References isn't as arbitrary or different from other languages as it might seem. It's really a way to specify l-values. When you assign to an object property, e.g., "o.x = 42", the l-value here is the "x" property of the "o" object. We need to capture both. In other languag

Re: Setting a property in the prototype chain?

On 11/04/2011, at 05:14, Mark S. Miller wrote: > > On Apr 10, 2011, at 22:18 , David Herman wrote: > > > function getDefiningObject(obj, key) { > >if (!(key in obj)) > >throw new Error("key " + key + " not found"); > >while (!obj.hasOwnProperty(key)) > > That should be > >

'this' is more complicated than I thought (PropertyReferences break equivalences)

Like most Javascript programmers, I have tended to follow a simple rule for functions using 'this': eta-expand method selections, use .bind, or get into trouble. Then I got curious about how method calls determine what object to pass as 'this': a method is a function selected from an object, a