urdf_model: don't use or define M_PI (#38)

urdf_model/include/urdf_model/pose.h

@@ -37,14 +37,6 @@
 #ifndef URDF_INTERFACE_POSE_H
 #define URDF_INTERFACE_POSE_H
 
-//For using the M_PI macro in visual studio it
-//is necessary to define _USE_MATH_DEFINES
-#ifdef _MSC_VER
-#ifndef _USE_MATH_DEFINES
-#define _USE_MATH_DEFINES
-#endif
-#endif
-
 #include <cmath>
 #include <sstream>
 #include <stdexcept>
@@ -126,12 +118,13 @@ class Rotation
 
     // Cases derived from https://orbitalstation.wordpress.com/tag/quaternion/
     double sarg = -2 * (this->x*this->z - this->w*this->y);
+    const double pi_2 = 1.57079632679489661923;
     if (sarg <= -0.99999) {
-      pitch = -0.5*M_PI;
+      pitch = -pi_2;
       roll  = 0;
       yaw   = 2 * atan2(this->x, -this->y);
     } else if (sarg >= 0.99999) {
-      pitch = 0.5*M_PI;
+      pitch = pi_2;
       roll  = 0;
       yaw   = 2 * atan2(-this->x, this->y);
     } else {