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% | Reference manual page: polygon_area_2.tex
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% | 21.06.2001   Author
% | Package: Polygon
% | 
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\begin{ccRefFunction}{polygon_area_2}  %% add template arg's if necessary

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%% \ccHtmlIndexC[function]{} %% add further index entries

\ccDefinition
  
The function \ccRefName\ computes the signed area of a polygon.

\ccInclude{CGAL/Polygon_2_algorithms.h}

\ccGlobalFunction{
template <class ForwardIterator, class Traits>
typename Traits::FT
polygon_area_2( ForwardIterator first, ForwardIterator last,
        const Traits& traits);}
{
Computes the signed area of the polygon defined by the range of points
\ccc{first} \ldots\ \ccc{last}.
The sign is positive for counterclockwise polygons, negative for
clockwise polygons. If the polygon is not simple, the area is not well defined.
}

\ccHeading{Requirements}
\ccIndexSubitem[C]{bottom_vertex_2}{requirements}
\begin{enumerate}
    \item \ccc{Traits} is a model of the concept 
	  PolygonTraits\_2\ccIndexMainItem[c]{PolygonTraits_2}.
	  Only the following members of this traits class are used:
          \begin{itemize}
	    \item \ccc{Compute_area_2} : Computes the signed area of the
	    oriented triangle defined by 3 \ccc{Point_2} passed as arguments.
            \item \ccc{FT}
            \item \ccc{compute_area_2_object}
          \end{itemize}
    \item \ccc{ForwardIterator::value_type} should be \ccc{Traits::Point_2},
\end{enumerate}

\ccSeeAlso

\ccRefIdfierPage{PolygonTraits_2} \\
\ccRefIdfierPage{CGAL::orientation_2} \\
\ccRefIdfierPage{CGAL::Polygon_2<PolygonTraits_2, Container>} \\

%% \ccIncludeExampleCode{examples/Polygon/polygon_area_2_prog.C}

\end{ccRefFunction}

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