View Compilation Error

0_0_23145861_6585.cpp: In member function 'void FFT::fft(int*, int*, int, int)':
0_0_23145861_6585.cpp:34:15: error: lvalue required as left operand of assignment
   a1[i].real()=0,b1[i].real()=0,
               ^
0_0_23145861_6585.cpp:34:30: error: lvalue required as left operand of assignment
   a1[i].real()=0,b1[i].real()=0,
                              ^
0_0_23145861_6585.cpp:35:15: error: lvalue required as left operand of assignment
   a1[i].imag()=0,b1[i].imag()=0;
               ^
0_0_23145861_6585.cpp:35:30: error: lvalue required as left operand of assignment
   a1[i].imag()=0,b1[i].imag()=0;
                              ^
0_0_23145861_6585.cpp:36:40: error: lvalue required as left operand of assignment
   for(int i=l;i<=mid;++i)a1[i-l].real()=c[i];
                                        ^
0_0_23145861_6585.cpp:37:38: error: lvalue required as left operand of assignment
   for(int i=0;i<=r-l;++i)b1[i].real()=d[i+1];
                                      ^