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\begin{ccRefClass}[Nef_polyhedron_S2<Traits>::]{Sphere_point}
\ccCreationVariable{p}

\ccDefinition

An object \ccc{p} of type \ccc{Sphere_point<R>} is a point on the
surface of a unit sphere. Such points correspond to the nontrivial
directions in space and similarly to the equivalence classes of all
nontrivial vectors under normalization.

\ccSetOneOfTwoColumns{5cm}

\ccTypes

\ccNestedType{RT}{ring number type.}

\ccSetOneOfTwoColumns{5cm}

\ccCreation

\ccConstructor{Sphere_point()}{ creates some sphere point.  }

\ccConstructor{Sphere_point(RT x, RT y, RT z)}{ creates a sphere
  point corresponding to the point of intersection of the ray starting
  at the origin in direction $(x,y,z)$ and the surface of $S_2$.  }

\ccSetTwoOfThreeColumns{4cm}{2cm}

\ccOperations

Access to the coordinates is provided by the following operations.
Note that the vector $(x,y,z)$ is not normalized.

\ccMethod{RT x() ;}{ the $x$-coordinate.  }

\ccMethod{RT y() ;}{ the $y$-coordinate.  }

\ccMethod{RT z() ;}{ the $z$-coordinate.  }

\ccMethod{bool operator==(const Sphere_point& q) ;}{Equality.}

\ccMethod{bool operator!=(const Sphere_point& q) ;}{Inequality.}

\ccMethod{Sphere_point antipode() ;}{returns the antipode of \ccc{p}.}

\end{ccRefClass}