/in/foo.cc: In function 'void FFT::FFT_init(int)':
/in/foo.cc:29:36: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
    rev_[i]=rev_[i/2]>>1|(i&1)<<lgn_-1;
                                ~~~~^~
/in/foo.cc: In function 'void FFT::FFT(FFT::C*)':
/in/foo.cc:39:53: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
    for(register int j=0;j<t;++j)ww[j]=omg_[j<<lgn_-i-1];
                                               ~~~~~~^~