C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  What's the difference between an object and a type? Goto page 1, 2  Next          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Dylan Guest Posted: Mon Dec 20, 2004 9:20 am    Post subject: What's the difference between an object and a type? thanks Back to top Jacques Labuschagne Guest Posted: Mon Dec 20, 2004 10:00 am    Post subject: Re: What's the difference between an object and a type? Dylan wrote: Quote: thanks An object is an instance of a type. Jacques. Back to top Jonathan Turkanis Guest Posted: Mon Dec 20, 2004 10:41 am    Post subject: Re: What's the difference between an object and a type? It's like the difference between a boxer and a weight class, or an employee and a job description. Jonathan Back to top Rafal 'Raf256' Maj Guest Posted: Mon Dec 20, 2004 12:45 pm    Post subject: Re: What's the difference between an object and a type? [email]spaldeen (AT) ontheball (DOT) com[/email] news:396ds0di29m3m8f64uo50bms7is3nn5vjh (AT) 4ax (DOT) com Quote: thanks The same as between "a humen" and "the Dylan". -- ~~~~=~~~~l_;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ _|___J ____, Pozdrawiam, moje www, C++, kontakt, itd.: X-( ssn256 ) Rafal Maj Raf256 - http://www.raf256.com/me-news/ ,"-------------" (strona w budowie) Back to top Rafal 'Raf256' Maj Guest Posted: Mon Dec 20, 2004 12:54 pm    Post subject: Re: What's the difference between an object and a type? [email]spaldeen (AT) ontheball (DOT) com[/email] news:396ds0di29m3m8f64uo50bms7is3nn5vjh (AT) 4ax (DOT) com Quote: thanks The same as between "a humen" and "the Dylan". typo... *human* -- ~~~~=~~~~l_;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ _|___J ____, Pozdrawiam, moje www, C++, kontakt, itd.: X-( ssn256 ) Rafal Maj Raf256 - http://www.raf256.com/me-news/ ,"-------------" (strona w budowie) Back to top Jon Bell Guest Posted: Mon Dec 20, 2004 1:59 pm    Post subject: Re: What's the difference between an object and a type? In article <396ds0di29m3m8f64uo50bms7is3nn5vjh (AT) 4ax (DOT) com>, Dylan <spaldeen (AT) ontheball (DOT) com> wrote: Quote: thanks object :: type == cookie :: cookie-cutter -- Jon Bell <jtbellm4h (AT) presby (DOT) edu> Presbyterian College Dept. of Physics and Computer Science Clinton, South Carolina USA Back to top Dave O'Hearn Guest Posted: Mon Dec 20, 2004 3:02 pm    Post subject: Re: What's the difference between an object and a type? What's the difference between "int" and "5"? The question is rather vague. I don't know if it has an answer. Philosophers have debated this stuff for thousands of years and show no sign of stopping soon. When inheritence comes in, it is important not to confuse the different relationships. The type-instance relationship is not the same as the base-derived relationship. Sometimes people will get sloppy and use the phrase "is a" to describe all these relationships, like 'file' is an fstream, fstream is an ifstream, etc. They are two different things. -- Dave O'Hearn Back to top Howard Guest Posted: Mon Dec 20, 2004 4:08 pm    Post subject: Re: What's the difference between an object and a type? "Dave O'Hearn" <daveoh77 (AT) pobox (DOT) com> wrote Quote: What's the difference between "int" and "5"? The question is rather vague. I don't know if it has an answer. Philosophers have debated this stuff for thousands of years and show no sign of stopping soon. They have? I don't recall any such discussions. For example, "what's the difference between 'human" and "Bob'?" One is a description/definition, the other names a specific instance. I see no confusion (or vagueness) here at all. An object is an instance of a type. A type is a description (a declaration), which follows very cleary defined rules in the C++ language. There are built-in types and user-defined types. Since this question is asked in the C++ language newsgoup, it seems pretty clear that these are the definitions asked for. Quote: When inheritence comes in, it is important not to confuse the different relationships. The type-instance relationship is not the same as the base-derived relationship. Sometimes people will get sloppy and use the phrase "is a" to describe all these relationships, like 'file' is an fstream, fstream is an ifstream, etc. They are two different things. -- That's a rather confusing analogy. The "is a" relationship described public inheritance, only. What this has to do with types and objects is, well, nothing as far as I can see...? Quote: Dave O'Hearn No offense intended, Dave, but I think you're just going to confuse the newbie here. Philosophy and C++ don't mix very well, in my opinion. :-) -Howard Back to top jeffc Guest Posted: Mon Dec 20, 2004 4:35 pm    Post subject: Re: What's the difference between an object and a type? "Howard" <alicebt (AT) hotmail (DOT) com> wrote Quote: When inheritence comes in, it is important not to confuse the different relationships. The type-instance relationship is not the same as the base-derived relationship. Sometimes people will get sloppy and use the phrase "is a" to describe all these relationships, like 'file' is an fstream, fstream is an ifstream, etc. They are two different things. -- That's a rather confusing analogy. The "is a" relationship described public inheritance, only. What this has to do with types and objects is, well, nothing as far as I can see...? Agreed. "Is a" makes sense in both contexts, even though it means 2 different things. Back to top Dave O'Hearn Guest Posted: Mon Dec 20, 2004 4:42 pm    Post subject: Re: What's the difference between an object and a type? Howard wrote: Quote: I see no confusion (or vagueness) here at all. An object is an instance of a type. A type is a description (a declaration), which follows very cleary defined rules in the C++ language. There are built-in types and user-defined types. Since this question is asked in the C++ language newsgoup, it seems pretty clear that these are the definitions asked for. Exactly. I see no confusion either, but the OP is confused. How? Quote: No offense intended, Dave, but I think you're just going to confuse the newbie here. Philosophy and C++ don't mix very well, in my opinion. Almost. I was trying to show the OP that his question was confusing, not to confuse the OP. The difference between a type and an object should be obvious to everyone, no technical background required. If it isn't obvious, there is probably some confusion in terms. But I can't guess what that confusion is. It would help if he asked a more specific question about objects and types. (Un)fortunately, if this is a homework, he may not be able to. -- Dave O'Hearn Back to top Dave O'Hearn Guest Posted: Mon Dec 20, 2004 5:09 pm    Post subject: Re: What's the difference between an object and a type? jeffc wrote: Quote: "Howard" <alicebt (AT) hotmail (DOT) com> wrote in message That's a rather confusing analogy. The "is a" relationship described public inheritance, only. What this has to do with types and objects is, well, nothing as far as I can see...? Agreed. "Is a" makes sense in both contexts, even though it means 2 different things. The FAQ has a whole section on confusions that arise from using "is a" to describe the derived-base relationship. http://www.parashift.com/c++-faq-lite/proper-inheritance.html The FAQ recommends "is substituable for", and describes it in terms of contracts. -- Dave O'Hearn Back to top Paavo Helde Guest Posted: Mon Dec 20, 2004 6:54 pm    Post subject: Re: What's the difference between an object and a type? An object takes up space in computer memory at runtime, a type does not. hth Paavo Back to top Howard Guest Posted: Mon Dec 20, 2004 7:42 pm    Post subject: Re: What's the difference between an object and a type? "Paavo Helde" <paavo (AT) ebi (DOT) ee> wrote Quote: An object takes up space in computer memory at runtime, a type does not. hth Paavo I don't think that's a good description, or even accurate. Computer memory is doled out by the operating system, and may be largely out of the control of the code as to exactly when and where it is allocated. But, regardless of the memory model used, what about member functions and static member data? Both of those exist independent of instances of a class (i.e., objects), since they are shared by all instances. So simply declaring a class or struct type may result in memory allocation for those members, separate from any instanciated objects of that type. -Howard Back to top Jonathan Mcdougall Guest Posted: Mon Dec 20, 2004 8:59 pm    Post subject: Re: What's the difference between an object and a type? Howard wrote: Quote: "Paavo Helde" <paavo (AT) ebi (DOT) ee> wrote in message An object takes up space in computer memory at runtime, a type does not. I don't think that's a good description, or even accurate. Computer memory is doled out by the operating system, and may be largely out of the control of the code as to exactly when and where it is allocated. Agree. Quote: But, regardless of the memory model used, what about member functions and static member data? Both of those exist independent of instances of a class (i.e., objects), since they are shared by all instances. So simply declaring a class or struct type may result in memory allocation for those members, separate from any instanciated objects of that type. Who said that? Jonathan Back to top jeffc Guest Posted: Mon Dec 20, 2004 9:03 pm    Post subject: Re: What's the difference between an object and a type? "Dave O'Hearn" <daveoh77 (AT) pobox (DOT) com> wrote Quote: jeffc wrote: "Howard" <alicebt (AT) hotmail (DOT) com> wrote in message That's a rather confusing analogy. The "is a" relationship described public inheritance, only. What this has to do with types and objects is, well, nothing as far as I can see...? Agreed. "Is a" makes sense in both contexts, even though it means 2 different things. The FAQ has a whole section on confusions that arise from using "is a" to describe the derived-base relationship. http://www.parashift.com/c++-faq-lite/proper-inheritance.html The FAQ recommends "is substituable for", and describes it in terms of contracts. I really see no reason for that, when it's perfectly natural in our regular speech to discuss it as is. A dog is an animal. Fido is a dog. What could be simpler? We don't go around saying "a dog is substitutable for an animal." Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Goto page 1, 2  Next Page 1 of 2   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.