View Compilation Error

0_0_31754407_19347.cpp:4:17: error: 'M_PI' was not declared in this scope
 const double pi=M_PI;
                 ^
0_0_31754407_19347.cpp: In function 'void FFT(X*, int)':
0_0_31754407_19347.cpp:19:26: error: 'w' was not declared in this scope
   for(int j=0;j<L>>1;j++,w=w*wn){
                          ^