text: #include <glm/ext/quaternion_trigonometric.hpp>
  #include <glm/ext/quaternion_float.hpp>
  #include <glm/ext/vector_relational.hpp>
  #include <glm/ext/scalar_relational.hpp>
  
  float const Epsilon = 0.001f;
  
  static int test_angle()
  {
  	int Error = 0;
  
  	{
  		glm::quat const Q = glm::quat(glm::vec3(1, 0, 0), glm::vec3(0, 1, 0));
  		float const A = glm::degrees(glm::angle(Q));
  		Error += glm::equal(A, 90.0f, Epsilon) ? 0 : 1;
  	}
  
  	{
  		glm::quat const Q = glm::quat(glm::vec3(0, 1, 0), glm::vec3(1, 0, 0));
  		float const A = glm::degrees(glm::angle(Q));
  		Error += glm::equal(A, 90.0f, Epsilon) ? 0 : 1;
  	}
  
  	{
  		glm::quat const Q = glm::angleAxis(glm::two_pi<float>() - 1.0f, glm::vec3(1, 0, 0));
  		float const A = glm::angle(Q);
  		Error += glm::equal(A, 1.0f, Epsilon) ? 1 : 0;
  	}
  
  	return Error;
  }
  
  int main()
  {
  	int Error = 0;
  
  	Error += test_angle();
  
  	return Error;
  }
  