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Top Forums Programming A trivial XOR doubt in a program Post 302247279 by royalibrahim on Wednesday 15th of October 2008 10:09:49 AM
Old 10-15-2008
A trivial XOR doubt in a program

Hi,

I am trying to reverse a string using the following program utilizing the Exclusive OR bit operation:

Code:
int main() {
   char str[] = "Quraish";
   char *p = str, temp;
   char *q = str + strlen(str) - 1;
   while ( p != q ) {
      if (*p != *q) {
         *p ^= *q; *q ^= *p; *p ^= *q;
      }
      p++; q--;
   }
   printf("%s \n", str);
}

The above code works perfectly alright, but if I change the line
Code:
*p ^= *q; *q ^= *p; *p ^= *q;

to
Code:
*p ^= *q ^= *p ^= *q;

(I am trying to do swapping inline)
it prints an empty string. Could anyone tell me why this behaviour is?
 

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curs_instr(3X)															    curs_instr(3X)

NAME
instr, innstr, winstr, winnstr, mvinstr, mvinnstr, mvwinstr, mvwinnstr - get a string of characters from a curses window SYNOPSIS
#include <curses.h> int instr(char *str); int innstr(char *str, int n); int winstr(WINDOW *win, char *str); int winnstr(WINDOW *win, char *str, int n); int mvinstr(int y, int x, char *str); int mvinnstr(int y, int x, char *str, int n); int mvwinstr(WINDOW *win, int y, int x, char *str); int mvwinnstr(WINDOW *win, int y, int x, char *str, int n); DESCRIPTION
These routines return a string of characters in str, extracted starting at the current cursor position in the named window. Attributes are stripped from the characters. The four functions with n as the last argument return a leading substring at most n characters long (exclu- sive of the trailing NUL). RETURN VALUE
All of the functions return ERR upon failure, or the number of characters actually read into the string. X/Open defines no error conditions. In this implementation, if the window parameter is null or the str parameter is null, a zero is returned. NOTES
Note that all routines except winnstr may be macros. PORTABILITY
SVr4 does not document whether a length limit includes or excludes the trailing NUL. The ncurses library extends the XSI description by allowing a negative value for n. In this case, the functions return the string ending at the right margin. SEE ALSO
curses(3X). curs_instr(3X)
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