View Compilation Error

0_0_21415676_28021.cpp:20:7: error: 'doubel' does not name a type
 const doubel pi= acos(-1.0);
       ^
0_0_21415676_28021.cpp: In function 'void fft(complex*, int, int)':
0_0_21415676_28021.cpp:70:27: error: 'pi' was not declared in this scope
   complex wn(cos(on * 2 * pi / k), sin(on * 2 * pi / k));//单位复根
                           ^