examples: improve the pendulum simulation, with several modes and diagrams (#13446)

examples/pendulum-simulation/modules/sim/vec_test.v

@@ -0,0 +1,64 @@
+module sim
+
+fn test_add() {
+	v := vector(
+		x: -0.016957230930171364
+		y: -0.02937078552673521
+		z: 0.002311063475327252
+	)
+	result := v + v
+	expected := vector(
+		x: -0.03391446186034273
+		y: -0.05874157105347042
+		z: 0.004622126950654504
+	)
+	assert result == expected
+}
+
+fn test_dot() {
+	v := vector(
+		x: -0.016957230930171364
+		y: -0.02937078552673521
+		z: 0.002311063475327252
+	)
+	result := v * v
+	expected := 0.0011555317376636305
+	assert result == expected
+}
+
+fn test_scale() {
+	v := vector(
+		x: -0.016957230930171364
+		y: -0.02937078552673521
+		z: 0.002311063475327252
+	)
+	result := v.scale(2.0)
+	expected := vector(
+		x: -0.03391446186034273
+		y: -0.05874157105347042
+		z: 0.004622126950654504
+	)
+	assert result == expected
+}
+
+fn test_norm_squared() {
+	v := vector(
+		x: -0.016957230930171364
+		y: -0.02937078552673521
+		z: 0.002311063475327252
+	)
+	result := v.norm_squared()
+	expected := 0.0011555317376636305
+	assert result == expected
+}
+
+fn test_norm() {
+	v := vector(
+		x: -0.016957230930171364
+		y: -0.02937078552673521
+		z: 0.002311063475327252
+	)
+	result := v.norm()
+	expected := 0.033993113091678295
+	assert result == expected
+}