1 files changed, 39 insertions, 0 deletions
diff --git a/src/haversine/listing_065.cpp b/src/haversine/listing_065.cpp
new file mode 100644
index 0000000..86e087c
--- /dev/null
+++ b/src/haversine/listing_065.cpp
@@ -0,0 +1,39 @@
+#include <math.h>
+
+static f64 Square(f64 A)
+{
+    f64 Result = (A*A);
+    return Result;
+}
+
+static f64 RadiansFromDegrees(f64 Degrees)
+{
+    f64 Result = 0.01745329251994329577 * Degrees;
+    return Result;
+}
+
+// NOTE(casey): EarthRadius is generally expected to be 6372.8
+static f64 ReferenceHaversine(f64 X0, f64 Y0, f64 X1, f64 Y1, f64 EarthRadius)
+{
+    /* NOTE(casey): This is not meant to be a "good" way to calculate the Haversine distance.
+       Instead, it attempts to follow, as closely as possible, the formula used in the real-world
+       question on which these homework exercises are loosely based.
+    */
+    
+    f64 lat1 = Y0;
+    f64 lat2 = Y1;
+    f64 lon1 = X0;
+    f64 lon2 = X1;
+    
+    f64 dLat = RadiansFromDegrees(lat2 - lat1);
+    f64 dLon = RadiansFromDegrees(lon2 - lon1);
+    lat1 = RadiansFromDegrees(lat1);
+    lat2 = RadiansFromDegrees(lat2);
+    
+    f64 a = Square(sin(dLat/2.0)) + cos(lat1)*cos(lat2)*Square(sin(dLon/2));
+    f64 c = 2.0*asin(sqrt(a));
+    
+    f64 Result = EarthRadius * c;
+    
+    return Result;
+}