Correct normalization of 0 vector

govector_test.go

@@ -58,4 +58,12 @@ func TestNormalize(t *testing.T) {
 	if vn.Mag() != 1 {
 		t.Errorf("Normalize Error")
 	}
+
+	v0 := Vector2d{0, 0}
+	vn0 := v0.Normalize()
+
+	if vn0.Mag() != 0 {
+		t.Errorf("Normalize Error")
+	}
+
 }

vectorpoint.go

@@ -44,6 +44,10 @@ func (v Vector2d) Scale(s float64) Vector2d {
 }
 
 func (v Vector2d) Normalize() Vector2d {
+	if v.X == 0 && v.Y == 0 {
+		return v
+	}
+
 	m := v.Mag()
 	return Vector2d{v.X / m, v.Y / m}
 }