C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  CompareWithoutRegardToCase          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message JKop Guest Posted: Mon Sep 27, 2004 10:55 am    Post subject: CompareWithoutRegardToCase Comments, Questions and Suggestions please! Returns true if strings are identical, returns false if strings are not identical. (without regard to case). bool CompareWithoutRegardToCase(const char* x, const char* y) { //Undefined Behaviour if supplied with null pointers ;-D if ( !*x || !*y ) //valid pointer to null string { if ( !*x && !*y ) return true; //2 null strings are equal. return false; } do { if ( tolower( static_cast<unsigned char>(*x) ) == tolower( static_cast<unsigned char>(*y) ) ) continue; else { return false; } } while ( (++x,++y) ,*x ); return !*y; } Back to top Buster Guest Posted: Mon Sep 27, 2004 3:51 pm    Post subject: Re: CompareWithoutRegardToCase JKop wrote: Quote: Comments, Questions and Suggestions please! Returns true if strings are identical, returns false if strings are not identical. (without regard to case). bool CompareWithoutRegardToCase(const char* x, const char* y) { //Undefined Behaviour if supplied with null pointers ;-D if ( !*x || !*y ) //valid pointer to null string { if ( !*x && !*y ) return true; //2 null strings are equal. return false; } do { if ( tolower( static_cast<unsigned char>(*x) ) == tolower( static_cast<unsigned char>(*y) ) ) continue; else { return false; } } while ( (++x,++y) ,*x ); return !*y; } What happens if the null-terminated string to which y points is longer than the one pointed to by x? bool CompareWithoutRegardToCase (char x, char y) { return std::tolower (static_cast <int> (x)) == std::tolower (static_cast <int> (y); } bool CompareWithoutRegardToCase (const char * x, const char * y) { // Undefined behaviour if supplied with null pointers while ((* x) && (* y) && CompareWithoutRegardToCase (* x, * y)) { ++ x; ++ y; } return ! ((* x) || (* y)); } -- Regards, Buster Back to top Buster Guest Posted: Mon Sep 27, 2004 3:54 pm    Post subject: Re: CompareWithoutRegardToCase Buster wrote: Quote: JKop wrote: .... What happens if the null-terminated string to which y points is longer than the one pointed to by x? You get the right answer, that's what. I'd still combine the initial test and the do-while into a while loop. Quote: -- Regards, Buster Back to top JKop Guest Posted: Mon Sep 27, 2004 5:48 pm    Post subject: Re: CompareWithoutRegardToCase Quote: What happens if the null-terminated string to which y points is longer than the one pointed to by x? The loop will detect that x's 'k' is not equal to y's '', and return false. Your point? -JKop Back to top JKop Guest Posted: Mon Sep 27, 2004 5:49 pm    Post subject: Re: CompareWithoutRegardToCase JKop posted: Quote: What happens if the null-terminated string to which y points is longer than the one pointed to by x? The loop will detect that x's 'k' is not equal to y's '', and return false. Your point? -JKop Opps, got mixed up there... The loop detects when it hits ''. -JKop Back to top Buster Guest Posted: Mon Sep 27, 2004 7:00 pm    Post subject: Re: CompareWithoutRegardToCase JKop wrote: Quote: JKop posted: What happens if the null-terminated string to which y points is longer than the one pointed to by x? The loop will detect that x's 'k' is not equal to y's '', and return false. Your point? Didn't you see my other message, the one where I pointed out my mistake? Quote: Opps, got mixed up there... The loop detects when it hits ''. Not that it matters, but you should say what "it" is. The point, anyway, is that you can use the same expression for the 'if' statement that you used as the 'while' condition of the do-while loop. That being done, you can replace the if statement and the do-while loop in your original code with a single while loop. -- Regards, Buster. Back to top Siemel Naran Guest Posted: Wed Sep 29, 2004 6:03 am    Post subject: Re: CompareWithoutRegardToCase "JKop" <NULL (AT) NULL (DOT) NULL> wrote Quote: Returns true if strings are identical, returns false if strings are not identical. (without regard to case). bool CompareWithoutRegardToCase(const char* x, const char* y) { //Undefined Behaviour if supplied with null pointers ;-D if ( !*x || !*y ) //valid pointer to null string { if ( !*x && !*y ) return true; //2 null strings are equal. return false; } do { if ( tolower( static_cast<unsigned char>(*x) ) == tolower( static_cast<unsigned char>(*y) ) ) continue; else { return false; } } while ( (++x,++y) ,*x ); return !*y; } Looks good, though the loop and return statement make it look more complicated than it really is (my version below looks simpler to me at least). Also, I don't think the cast to unsigned char is necessary. In the code below, I've also stored the result of *x in a variable of type char so as to avoid additional memory lookups due to aliasing -- but I wonder how much this improves performance. Your comments are very good too, but I left them out to save space. bool CompareWithoutRegardToCase(const char* xx, const char* yy) { for ( ; ; ++xx, ++yy) { char x = tolower(*xx); char y = tolower(*yy); if (x != y) return false; if (!x && !y) return true; } return false; // never reached } Be aware that there is std::equal of 5 arguments in #include <algorithm>. std::equal(a, a+strlen(a), b, b+strlen(b), eqnocase()); where struct eqnocase { bool operator()(char lhs, char rhs) const { return tolower(lhs) == tolower(rhs); } }; The next exercise is to write a CompareWithoutRegardToCase that returns an int: < 0 if lhs < rhs, 0 if lhs == rhs, >0 if lhs > rhs. Wait a sec, is that the convention of strcmp (I always get confused and have to look it up)? Some implementations already provide this function with the name stricmp, but it's not part of the standard. 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.