C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  pointer in C++          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Bob Keith Guest Posted: Fri Jun 27, 2003 6:48 pm    Post subject: pointer in C++ I am a beginner. So this question could be very stupid. I am not very clear about the pointer in C++, would anyone let me know the difference of the following usage of pointer. int* a int *a int &a int& a int*& a Many thanks. Back to top Stuart Golodetz Guest Posted: Fri Jun 27, 2003 7:05 pm    Post subject: Re: pointer in C++ "Bob Keith" <structuralvibration (AT) yahoo (DOT) com> wrote Quote: I am a beginner. So this question could be very stupid. I am not very clear about the pointer in C++, would anyone let me know the difference of the following usage of pointer. int* a // a is a pointer to an int int *a // a is again a pointer to an int int &a // a is a reference to an int int& a // a is again a reference to an int int*& a // a is a reference to a pointer to an int HTH, Stuart. Quote: Many thanks. Back to top Victor Bazarov Guest Posted: Fri Jun 27, 2003 7:09 pm    Post subject: Re: pointer in C++ "Bob Keith" <structuralvibration (AT) yahoo (DOT) com> wrote... Quote: I am a beginner. So this question could be very stupid. I am not very clear about the pointer in C++, would anyone let me know the difference of the following usage of pointer. int* a int *a The two declarations above are the same and declare 'a' a pointer to an int. Quote: int &a int& a The two declarations above are the same and declare 'a' a reference to an int (no pointers here). Quote: int*& a This declaration declares 'a' a reference to a pointer to an int. All three last declarations require initialisation if they are also definitions. Sounds convoluted? It is, sort of. If your declaration is in the namespace scope or in a function scope, they are also definitions. And any definition of a reference requires an initialiser. int *& rpa; // error - lacks initialiser (namespace scope) int main() { int& a; // error - lacks initialiser (function scope) } Quote: Many thanks. Many welcomes. Victor Back to top Ron Natalie Guest Posted: Fri Jun 27, 2003 7:33 pm    Post subject: Re: pointer in C++ "Bob Keith" <structuralvibration (AT) yahoo (DOT) com> wrote Quote: I am a beginner. So this question could be very stupid. I am not very clear about the pointer in C++, would anyone let me know the difference of the following usage of pointer. int* a int *a int &a int& a int*& a Half of those aren't pointers. The arrangement of the white space is not significant. Back to top Sin Guest Posted: Fri Jun 27, 2003 7:36 pm    Post subject: Re: pointer in C++ Quote: I am not very clear about the pointer in C++, would anyone let me know the difference of the following usage of pointer. Sure Quote: int* a int *a Same exact thing. Should it be on a, or on int? It doensn't change a thing as far as the compiler is concerned and for clarity there are arguments on both sides. The important thing to know is that "int *a, b;" will declare a int pointer (a) and an integer (b), rather than two pointers... As for what a pointer is, it's simply a placeholder for an address... Ex: int v= 12; int *a= &v; int *b= &v int *c= &v; *a= 13; // At this point, v == 13, *a == 13, *b == 13 and *c == 13 Quote: int &a int& a Again, both are the same. They are NOT pointers though they are references. A reference is similar to a pointer, but it's actually just a variable that shares the same address as the object it's initialized with. It makes their use easier for the non initiated, I guess, but it lacks the possibility of being set to nothing (NULL). Ex: int v= 12; int &a= v; int &b= v; int &c= v; a= 13; // At this point, v == 13, a == 13, b == 13 and c == 13 Quote: int*& a That would be a reference to a pointer... Ex: int v= 12; int &r= v; int *p= &r; int *&rp= p; *rp= 13; // At this point, v == 13, r == 13, *p == 13, **rp == 13 In my opinion references should be avoided unless necessary. I mostly do C with occasionnal C++ and I can count on the fingers of one hand the times I had to use references in the past 5 years... Alex. Back to top Ron Natalie Guest Posted: Fri Jun 27, 2003 10:34 pm    Post subject: Re: pointer in C++ "Howard" <alicebt (AT) hotmail (DOT) com> wrote Quote: "Ron Natalie" <ron (AT) sensor (DOT) com> wrote in message news:KdydnbiyyshyBmGjXTWQlg (AT) giganews (DOT) com... int* a int *a int &a int& a int*& a Half of those aren't pointers. Half? So, say, 2.5 of those 5 variables are (or are not) pointers? Perhaps this is new math? Sure, the reference to a pointer counts as half :-) Back to top Jakob Bieling Guest Posted: Thu Jul 17, 2003 10:51 pm    Post subject: Re: pointer in C++ "Yuh-Horng Shiau" <yhshiau (AT) mail (DOT) nuu.edu.tw> wrote Quote: The declaration of 'int *& a;' will get an error from the compiler. 'int*& a;' will give you an error yes, because you are not initializing the reference. Just like 'int& a;' will give you an error. The following is valid: int* b = 0; int*& a = b; regards -- jb (replace y with x if you want to reply by e-mail) 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.