View Compilation Error

0_0_20338328_3490.cpp: In function 'Comp getRevRotateFactor(unsigned int)':
0_0_20338328_3490.cpp:85:20: error: 'M_PI' was not declared in this scope
   return exp(-2. * M_PI / size * Comp(0, 1));
                    ^
0_0_20338328_3490.cpp: In function 'Comp getRotateFactor(unsigned int)':
0_0_20338328_3490.cpp:89:19: error: 'M_PI' was not declared in this scope
   return exp(2. * M_PI / size * Comp(0, 1));
                   ^