View Compilation Error

0_0_18449682_24107.cpp: In function 'int bitcount(int)':
0_0_18449682_24107.cpp:14:59: error: 'x' was not declared in this scope
 inline int bitcount(int s) { return s == 0 ? 0 : bitcount(x&(x-1)) +1; }
                                                           ^