View Compilation Error

0_0_13587939_30265.cpp: In function 'void fft(base*, int, double)':
0_0_13587939_30265.cpp:51:51: error: lvalue required as left operand of assignment
         for (int i = 0; i < len; i++) a[i].real() = a[i].real() / len;
                                                   ^