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Task/Haversine-formula/Sidef/haversine-formula.sidef

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+class EarthPoint(lat, lon) {
+
+    const earth_radius = 6371;       # mean earth radius
+    const radian_ratio = Math.pi/180;
+
+    # accessors for radians
+    method latR { self.lat * radian_ratio };
+    method lonR { self.lon * radian_ratio };
+
+    method haversine_dist(EarthPoint p) {
+        var arc = EarthPoint(
+              self.lat - p.lat,
+              self.lon - p.lon,
+        );
+
+        var a = Math.sum(
+                  (arc.latR / 2).sin**2,
+                  (arc.lonR / 2).sin**2 *
+                    self.latR.cos * p.latR.cos
+                )
+
+        earth_radius * a.sqrt.asin * 2;
+    }
+}
+
+var BNA = EarthPoint.new(lat: 36.12, lon: -86.67);
+var LAX = EarthPoint.new(lat: 33.94, lon: -118.4);
+
+say BNA.haversine_dist(LAX);   # => 2886.44444283798329974715782394574672