Singleton vs Singleton
in [JavaScript]
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From: Garrett Smith on 27 Jan 2010 02:18 Thomas 'PointedEars' Lahn wrote: > Garrett Smith wrote: > >> Thomas 'PointedEars' Lahn wrote: >>> Garrett Smith wrote: >>>> Scott Sauyet wrote: >>>>> On Jan 25, 3:50 pm, Asen Bozhilov <asen.bozhi...(a)gmail.com> wrote: >>>>>> I want Singleton with properties: >>>>>> - Doesn't have constructor I take it he wants a Singleton without a constructor property. Did I get that wrong? >>>> Why not? >>> The question is pointless; it simply cannot be done. Every object >>> has a constructor, even those created with initializers. >> Not every object will have constructor. > > True. > >> Even if changed to "Every native object", it would still not be true. > > True, the Global Object makes an exception there. There is no description > in the Specification how it is created; it is simply "created before > control enters any execution context" and then it "is there". > >> Even if changed to "Every object except the global object," it would >> still not be true. > > Yes, it would. While maybe not accessible from ECMAScript code, host > objects need to have a constructor somewhere by which they have been > constructed. > A host object is not required to have a constructor; not at least as far as a program is concerned. I did interpret Asen's meaning of "I want Singleton with properties: - Doesn't have constructor" to mean that the object would not have a constructor property. I can't think of any reason why he would be making program requirements about unobservable implementation details. It sounds like you are interpreting the word "constructor" in general sense, to mean the thing that was new'd, and then further broadening that to include the implementation details of the Host. That seems to be broadening context of the discussion. That is not what I interpreted. I read Asen's message as meaning "constructor" property, and as something observable by ECMAScript. An ECMAScript engine's implementation language is not something that the ECMA-262 gets to decide upon. That language is not required to have constructors, and so although the implementation most likely does (C, C++, Java), it is neither required nor observable. >> A new'd object automatically gets a [[Prototype]] from the object that >> constructed it. The constructor comes from that. > > No, the constructor needs to exist before. > My sentence is referring to the `constructor` property. The examples I posted follow that. Now if by "constructor" you mean not constructor property, but the (function) object that implements [[Construct]]. If we are talking about Object, it might be the case that Object is not present. There is some sort of primordial preservation in implementations. I am using the term "primordial" to describe what is built-in, but internally preserved. I got this term from reading es-discuss subject "Module isolation". (function(){ Object = null; return ({}).constructor; })(); Results null; The obvious observation, however, is that object *was* created, and so it may seem odd that the object's constructor property points to global Object, which is null, yet the the object is created "as if by the expression `new Object`. As a bookmarklet: javascript: alert( function(){Object = null;return ({ ctor : Object}).ctor;}() ) elerts "null" The result shows that the object is created. This happens "as if by the expression `new Object()`". The object literal has a constructor property that points to Object, which is null (AISB). >> The global object's [[Prototype]] is implementation dependent, so it >> might have any [[constructor. [...] > > I was not talking about the `constructor' property. You miss the point. > Did I? I thought the point was to create a Singleton without a constructor property. Asen - what was your meaning? -- Garrett comp.lang.javascript FAQ: http://jibbering.com/faq/
From: Asen Bozhilov on 27 Jan 2010 09:59 Garrett Smith wrote: > Did I? I thought the point was to create a Singleton without a > constructor property. Asen - what was your meaning? I mean: - Doesn't have [[Construct]] method and `Singleton` cannot be use as part of `new Singleton()` expression.
From: Scott Sauyet on 27 Jan 2010 10:31 On Jan 27, 9:59 am, Asen Bozhilov <asen.bozhi...(a)gmail.com> wrote: > Garrett Smith wrote: >> Did I? I thought the point was to create a Singleton without a >> constructor property. Asen - what was your meaning? > > I mean: > > - Doesn't have [[Construct]] method and `Singleton` cannot be use as > part of `new Singleton()` expression. It's not clear to me, though, if any of the suggestions made in this thread -- Thomas Lahn's, mine, or your own -- meet your needs. Are you still looking for a solution to your problem or have you found one? I know you're not the OP, but it's your criteria that has generated most of the discussion. -- Scott
From: Thomas 'PointedEars' Lahn on 27 Jan 2010 12:44 Garrett Smith wrote: > Thomas 'PointedEars' Lahn wrote: >> Garrett Smith wrote: >>> Thomas 'PointedEars' Lahn wrote: >>>> Garrett Smith wrote: >>>>> Scott Sauyet wrote: >>>>>> On Jan 25, 3:50 pm, Asen Bozhilov <asen.bozhi...(a)gmail.com> wrote: >>>>>>> I want Singleton with properties: >>>>>>> - Doesn't have constructor > > I take it he wants a Singleton without a constructor property. Did I get > that wrong? I do not know. He did not write `constructor *property*', so ... >>>>> Why not? >>>> The question is pointless; it simply cannot be done. Every object >>>> has a constructor, even those created with initializers. >>> Not every object will have constructor. >> >> True. >> >>> Even if changed to "Every native object", it would still not be true. >> >> True, the Global Object makes an exception there. There is no >> description in the Specification how it is created; it is simply >> "created before control enters any execution context" and then it "is >> there". >> >>> Even if changed to "Every object except the global object," it would >>> still not be true. >> >> Yes, it would. While maybe not accessible from ECMAScript code, host >> objects need to have a constructor somewhere by which they have been >> constructed. > > A host object is not required to have a constructor; not at least as far > as a program is concerned. If by "program" you mean _ECMAScript_ /Program/, then you are right; otherwise not. > I did interpret Asen's meaning of "I want Singleton with properties: - > Doesn't have constructor" to mean that the object would not have a > constructor property. Yes, that is one possible interpretation. ISTM that the habit of East Europeans of omitting articles in English is getting in the way here. > I can't think of any reason why he would be making program requirements > about unobservable implementation details. The details do not have to be finally unobservable. AISB, objects created with initializers have a constructor, too. The constructor of {} is (the Function instance referred to by Object), the constructor of [] is Array, and the constructor of /./ is RegExp; regardless whether there is a `constructor' property on the instance or its prototype chain to refer to it. If he would not be aware of that, this might be the reason for this rather weird requirement of his (it would be a user-defined object and AI(SH)SB, every user-defined object has a constructor). > It sounds like you are interpreting the word "constructor" in general > sense, to mean the thing that was new'd, and then further broadening > that to include the implementation details of the Host. That seems to be > broadening context of the discussion. ISTM this discussion and all your examples are pointless without Asen saying what he really meant. > That is not what I interpreted. I read Asen's message as meaning > "constructor" property, and as something observable by ECMAScript. Yes, I got that already. No need of preaching to the choir ;-) > An ECMAScript engine's implementation language is not something that the > ECMA-262 gets to decide upon. That language is not required to have > constructors, and so although the implementation most likely does (C, > C++, Java), it is neither required nor observable. However, if it is an *object*, it must have a constructor, regardless of the programming language. That is how OOP works. Even the ECMAScript Global Object needs to be constructed somehow -- it does not just appear out of thin air. PointedEars -- realism: HTML 4.01 Strict evangelism: XHTML 1.0 Strict madness: XHTML 1.1 as application/xhtml+xml -- Bjoern Hoehrmann
From: Asen Bozhilov on 27 Jan 2010 13:43 Thomas 'PointedEars' wrote: > Yes, that is one possible interpretation. ISTM that the habit of East > Europeans of omitting articles in English is getting in the way here. You are right about my English. I know for people which English is native, is very hard to reading my posts. Maybe if i read on my native language - Bulgarian someone, which write like my on English i will be ignoring. For East Europeans is hard to learn English, because languages here and English are very different languages. However, i make every endeavour to learn English and i hope soon my English to be a better. I will be glad to write here without confusions like this. Apologize to all members of c.l.js. > ISTM this discussion and all your examples are pointless without Asen > saying what he really meant. I was write already. I'm not meant `constructor` property, which is resolve from Prototype chain. I mean internal [[Construct]] method. I don't want `object' referring from `Singleton` to be used as part of `new Singleton();` expression. Object literal allow me to do it that.
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