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Shoelace formula for polygonal area: Difference between revisions
Add Swift
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30
</pre>
=={{header|Swift}}==
{{trans|Scala}}
<lang swift>import Foundation
struct Point {
var x: Double
var y: Double
}
extension Point: CustomStringConvertible {
var description: String {
return "Point(x: \(x), y: \(y))"
}
}
struct Polygon {
var points: [Point]
var area: Double {
let xx = points.map({ $0.x })
let yy = points.map({ $0.y })
let overlace = zip(xx, yy.dropFirst() + yy.prefix(1)).map({ $0.0 * $0.1 }).reduce(0, +)
let underlace = zip(yy, xx.dropFirst() + xx.prefix(1)).map({ $0.0 * $0.1 }).reduce(0, +)
return abs(overlace - underlace) / 2
}
init(points: [Point]) {
self.points = points
}
init(points: [(Double, Double)]) {
self.init(points: points.map({ Point(x: $0.0, y: $0.1) }))
}
}
let poly = Polygon(points: [
(3,4),
(5,11),
(12,8),
(9,5),
(5,6)
])
print("\(poly) area = \(poly.area)")</lang>
{{out}}
<pre>Polygon(points: [Point(x: 3.0, y: 4.0), Point(x: 5.0, y: 11.0), Point(x: 12.0, y: 8.0), Point(x: 9.0, y: 5.0), Point(x: 5.0, y: 6.0)]) area = 30.0</pre>
=={{header|TI-83 BASIC}}==
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