View Compilation Error

0_0_21732706_18372.cpp: In function 'double rev(double)':
0_0_21732706_18372.cpp:10:12: error: 'M_PI' was not declared in this scope
 #define pi M_PI
            ^
0_0_21732706_18372.cpp:34:24: note: in expansion of macro 'pi'
  if (t < 0) return t + pi;
                        ^
0_0_21732706_18372.cpp:10:12: error: 'M_PI' was not declared in this scope
 #define pi M_PI
            ^
0_0_21732706_18372.cpp:35:13: note: in expansion of macro 'pi'
  return t - pi;
             ^
0_0_21732706_18372.cpp: In function 'int main()':
0_0_21732706_18372.cpp:10:12: error: 'M_PI' was not declared in this scope
 #define pi M_PI
            ^
0_0_21732706_18372.cpp:52:24: note: in expansion of macro 'pi'
   l = v[1]; r = v[1] + pi;
                        ^