C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How do I write this in pointer notation?          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Angela Guest Posted: Sun Oct 26, 2003 9:51 pm    Post subject: How do I write this in pointer notation? //array notation works*********** char temp[] for(int x=0; x { temp[x]=(temp[x]*2); } //simple char encoding //how do I do the same thing with pointer notation********** char* temp while( *temp ) { *temp++= (*temp)*2; } //simple char encoding I have played around with this and usually it just erases the first few letters. If I wanted to do something like this with a C++ string, is this possible? Back to top lilburne Guest Posted: Sun Oct 26, 2003 10:49 pm    Post subject: Re: How do I write this in pointer notation? Angela wrote: Quote: //array notation works*********** char temp[] for(int x=0; x { temp[x]=(temp[x]*2); } //simple char encoding //how do I do the same thing with pointer notation********** char* temp while( *temp ) { *temp++= (*temp)*2; } //simple char encoding I have played around with this and usually it just erases the first few letters. If I wanted to do something like this with a C++ string, is this possible? { *temp++= (*temp)*2; } //simple char encoding The *temp++ has the side effect of incrementing temp, so the temp on the left is not the same as the temp on the right. *temp++ *= 2; Back to top Artie Gold Guest Posted: Mon Oct 27, 2003 2:12 am    Post subject: Re: How do I write this in pointer notation? Angela wrote: Quote: //array notation works*********** char temp[] for(int x=0; x { temp[x]=(temp[x]*2); } //simple char encoding //how do I do the same thing with pointer notation********** char* temp while( *temp ) { *temp++= (*temp)*2; } //simple char encoding You cannot do it this way; the value of `temp' is being altered without an intervening sequence point causing undefined behavior. One correct option would be to mimic the array form, as in: for (; *temp; temp++) *temp = *temp * 2; Quote: I have played around with this and usually it just erases the first few letters. Yes, due to the invocation of undefined behavior noted above. Quote: If I wanted to do something like this with a C++ string, is this possible? Yes. Certainly. (Look up `iterator' and `transform', for example) HTH, --ag -- Artie Gold -- Austin, Texas Oh, for the good old days of regular old SPAM. Back to top Artie Gold Guest Posted: Mon Oct 27, 2003 2:14 am    Post subject: Re: How do I write this in pointer notation? lilburne wrote: [snip] Quote: { *temp++= (*temp)*2; } //simple char encoding The *temp++ has the side effect of incrementing temp, so the temp on the left is not the same as the temp on the right. *temp++ *= 2; Better than my original reply! (on this point) Quote: --ag -- Artie Gold -- Austin, Texas Oh, for the good old days of regular old SPAM. Back to top        C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1 Powered by phpBB © 2001, 2006 phpBB Group