@prefix math: <http://www.w3.org/2000/10/swap/math#>.
@prefix e: <http://eulersharp.sourceforge.net/2003/03swap/log-rules#>.
@prefix polygon: <https://eyereasoner.github.io/eye/reasoning/polygon#>.

{(?POINT) polygon:area 0} <= true.
{?POINTS polygon:area ?AREA} <= {
    ?POINTS e:firstRest ((?X1 ?Y1) ?POINTS1).
    ?POINTS1 e:firstRest ((?X2 ?Y2) ?POINTS2).
    ?POINTS1 polygon:area ?AREA1.
    ((((?X1 ?Y2)!math:product (?Y1 ?X2)!math:product)!math:difference 2)!math:quotient ?AREA1) math:sum ?AREA.
}.
