Shoelace formula for polygonal area: Difference between revisions
Add Cowgol
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<pre>30</pre>
=={{header|Cowgol}}==
<lang cowgol>include "cowgol.coh";
typedef Coord is uint16; # floating point types are not supported
record Point is
x: Coord;
y: Coord;
end record;
sub shoelace(p: [Point], length: intptr): (area: Coord) is
var left: Coord := 0;
var right: Coord := 0;
var y0 := p.y;
var x0 := p.x;
while length > 1 loop
var xp := p.x;
var yp := p.y;
p := @next p;
left := left + xp * p.y;
right := right + yp * p.x;
length := length - 1;
end loop;
left := left + y0 * p.x;
right := right + x0 * p.y;
if left < right then
area := right - left;
else
area := left - right;
end if;
area := area / 2;
end sub;
var polygon: Point[] := {{3,4},{5,11},{12,8},{9,5},{5,6}};
print_i16(shoelace(&polygon[0], @sizeof polygon));
print_nl();</lang>
{{out}}
<pre>30</pre>
=={{header|D}}==
<lang D>import std.stdio;
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