\begin{ccRefFunction}{leftturn}

\ccFunction{bool leftturn(const Point_2<R> &p,
                          const Point_2<R> &q,
                          const Point_2<R> &r);}
{returns \ccc{true} iff \ccc{p}, \ccc{q}, and \ccc{r} form a left turn.}
\end{ccRefFunction}