C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  confusion involving pointer to pointer when converting from          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Kavya Guest Posted: Sat Dec 23, 2006 10:10 am    Post subject: confusion involving pointer to pointer when converting from Since Circle is-a Shape we are allowed to do this Circle *c = new Circle; Shape *s = c; //Works But we can't do this Circle **cc = &c; Shape **ss = cc; //Does not works Similarly, we can convert a pointer to non-const to a pointer to const but we may not convert a pointer to pointer to non-const to a pointer to pointer to const: char *s1 = 0; const char *s2 = s1; // works. char *a[MAX]; const char **ps = a; // Does not works Can someone explain this? Back to top Gianni Mariani Guest Posted: Sat Dec 23, 2006 10:11 am    Post subject: Re: confusion involving pointer to pointer when converting f Kavya wrote: Quote: Since Circle is-a Shape we are allowed to do this Circle *c = new Circle; Shape *s = c; //Works But we can't do this Circle **cc = &c; Shape **ss = cc; //Does not works If this were to work, you would be able to do this: Circle *c = new Circle; Tri *t = new Tri; Circle **cc = &c; Shape **ss = cc; * ss = t; c.radius = 22; // OOOPS - undefined behaviour which is not very desirable. Quote: Similarly, we can convert a pointer to non-const to a pointer to const but we may not convert a pointer to pointer to non-const to a pointer to pointer to const: char *s1 = 0; const char *s2 = s1; // works. char *a[MAX]; const char **ps = a; // Does not works Can someone explain this? Same thing. char *s1 = 0; const char foo[] = "FOO"; const char **ps = &s1; // is not allowed *ps = foo; // s1 now points to foo s1[0]='B'; // assigning a const char - not good. 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.