Add helpers based on Slice: row(), col(), xy()

test/vector3.cpp

@@ -27,6 +27,29 @@ int main()
     TEST(isEqual(a.unit(), a.normalized()));
     TEST(isEqual(a*2.0, Vector3f(2, 0, 0)));
 
+    Vector2f g2(1,3);
+    Vector3f g3(7, 11, 17);
+    g3.xy() = g2;
+    TEST(isEqual(g3, Vector3f(1, 3, 17)));
+
+    const Vector3f g4(g3);
+    Vector2f g5 = g4.xy();
+    TEST(isEqual(g5,g2));
+    TEST(isEqual(g2,Vector2f(g4.xy())));
+
+    Vector3f h;
+    TEST(isEqual(h,Vector3f(0,0,0)));
+
+    Vector<float, 4> j;
+    j(0) = 1;
+    j(1) = 2;
+    j(2) = 3;
+    j(3) = 4;
+
+    Vector3f k = j.slice<3,1>(0,0);
+    Vector3f k_test(1,2,3);
+    TEST(isEqual(k,k_test));
+
     return 0;
 }