% begin cgal manual page

\begin{ccRefClass}{Sphere_direction<R>}\ccCreationVariable{d}

\ccDefinition

An object \ccc{c} of type \ccc{Sphere_direction<R>} is a direction on
the surface of the unit sphere.  Such directions can be used to
describe walks that are part of great circles.

\ccSetOneOfTwoColumns{5cm}

\ccTypes

\ccNestedType{R}{representation class.}

\ccNestedType{RT}{ring type.}

\ccSetOneOfTwoColumns{5cm}

\ccCreation

\ccConstructor{Sphere_direction<R>()}{creates some direction.}

\ccConstructor{Sphere_direction<R>(Sphere_circle<R> c)}{ creates the
  direction corresponding to the circle \ccc{c}.  }

\ccConstructor{Sphere_direction<R>(Sphere_point<R> p, Sphere_point<R>
  q)}{ creates a direction that describes the orientation of the great
  circle through $p$ and $q$ (oriented such that the segment $pq$ is
  the shorter one of the two possible ones. \ccPrecond $p$ and $q$ are
  not opposite on $S_2$.  }

\ccSetTwoOfThreeColumns{4cm}{2cm}

\ccOperations

\ccMethod{Sphere_direction<R> opposite() ;}{returns the opposite of
  \ccc{d}.  }

\end{ccRefClass}