C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  reference variable and local variable          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Kench Guest Posted: Mon Jun 28, 2004 4:48 pm    Post subject: reference variable and local variable I was curious and playing with pointers and references to see what's different between them. Other than the obvious ones involving C++ syntax & things like references cannot be modified with addition & subtraction, pointers can be modified, both are similar. It stated me going what are the diferrence between a reference vairable and local variable ? Here are what I can think of 1. For a local variable constructor is called, not the case for a reference variable. 2. Local variable cannot be NULL. Reference variable can point to a NULL object by a simple trick like. Employee* e = NULL; Employee* ref = *e; Anything else? Back to top Howard Guest Posted: Mon Jun 28, 2004 5:07 pm    Post subject: Re: reference variable and local variable "Kench" <none (AT) none (DOT) com> wrote Quote: I was curious and playing with pointers and references to see what's different between them. Other than the obvious ones involving C++ syntax & things like references cannot be modified with addition & subtraction, pointers can be modified, both are similar. It stated me going what are the diferrence between a reference vairable and local variable ? Here are what I can think of 1. For a local variable constructor is called, not the case for a reference variable. 2. Local variable cannot be NULL. Reference variable can point to a NULL object by a simple trick like. Employee* e = NULL; Employee* ref = *e; Anything else? I'm puzzled why you're using the term "local" at all. The term "local variable" indicates a variable declared in local scope, i.e., inside a function. That has nothing to do with the type of variable (i.e., built-in, user-defined, pointer, or reference). Also, you refer to a reference, but your example (Empoyee*) is a pointer. Which did you mean? Given these discrepencies, I won't comment on your points, because they don't make sense without my making assumptions about what I *think* you meant. Your best bet is to read a good C++ book. There should be plenty of information about pointer-type variables and reference-type variables. Then come back here and we'd be glad to help clear up any specific points, once you have the terminology correct so we know what you mean. -Howard Back to top Victor Bazarov Guest Posted: Mon Jun 28, 2004 5:49 pm    Post subject: Re: reference variable and local variable Kench wrote: Quote: I was curious and playing with pointers and references to see what's different between them. Other than the obvious ones involving C++ syntax & things like references cannot be modified with addition & subtraction, pointers can be modified, both are similar. "both are similar" is an incomplete statement. Both are similar to what? If you wanted to state that they are similar, you should not have used the word "both". Quote: It stated me going what are the diferrence between a reference vairable and local variable ? A "reference variable" is what is known as "an alias", a different way to refer (lacking a better word) to an object. Quote: Here are what I can think of 1. For a local variable constructor is called, not the case for a reference variable. The constructor is called for an object, not for a variable. Quote: 2. Local variable cannot be NULL. Only pointers can be NULL. Quote: Reference variable can point to a NULL object by a simple trick like. Employee* e = NULL; Employee* ref = *e; This is not a "trick", it is a well known way to cause _undefined_ behaviour. Dereferencing a NULL pointer is _not_ allowed. So, in a valid C++ program there can be no "NULL" references. Quote: Anything else? A variable can have a type "reference to T", where T designates another type. There are special restrictions to what T could be. However, nothing precludes a variable from being a reference and local at the same time. Victor 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 Page 1 of 1   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.