Fix LatLng::operator== to treat ±180° longitude as equal

Author: gistrec

include/LatLng.hpp

@@ -35,15 +35,22 @@ class LatLng {
     LatLng& operator=(const LatLng & other) = default;
 
     bool operator==(const LatLng & other) const {
-        return isCoordinateEqual(lat, other.lat) && 
-               isCoordinateEqual(lng, other.lng);
+        return isCoordinateEqual(lat, other.lat) &&
+               isLngEqual(lng, other.lng);
     }
 
 
 private:
     bool isCoordinateEqual(double first, double second) const {
         return std::fabs(first - second) < 1e-12;
     }
+
+    // Longitude wraps: 180° and -180° are the same meridian.
+    bool isLngEqual(double a, double b) const {
+        double diff = std::fabs(std::fmod(a - b, 360.0));
+        if (diff > 180.0) diff = 360.0 - diff;
+        return diff < 1e-12;
+    }
 };
 
 #endif // GEOMETRY_LIBRARY_LATLNG

tests/LatLng/operator_equal.hpp

@@ -0,0 +1,16 @@
+#include <gtest/gtest.h>
+
+#include "LatLng.hpp"
+
+TEST(LatLng, operator_equal) {
+    // Basic equality and inequality
+    EXPECT_TRUE (LatLng( 0,  0) == LatLng( 0,  0));
+    EXPECT_FALSE(LatLng( 0,  0) == LatLng( 1,  0));
+    EXPECT_FALSE(LatLng( 0,  0) == LatLng( 0,  1));
+    EXPECT_FALSE(LatLng( 1,  0) == LatLng(-1,  0));
+
+    // ±180° is the same meridian
+    EXPECT_TRUE(LatLng(  0,  180) == LatLng(  0, -180));
+    EXPECT_TRUE(LatLng( 45,  180) == LatLng( 45, -180));
+    EXPECT_TRUE(LatLng(-45,  180) == LatLng(-45, -180));
+}

tests/Tests.cpp

@@ -1,4 +1,6 @@
 /** Including all tests */
+#include "LatLng/operator_equal.hpp"
+
 #include "MathUtil/mod.hpp"
 
 #include "SphericalUtil/interpolate.hpp"