[Lang] support v.x/v.y/v.z/v.w for easy Vector subscript (#1133)

* [Lang] support v.x, v.y, v.z for easy Vector subscript

* [skip ci] Proxy.xyzw, add test

* fix test_cli

* [skip ci] enforce code format

Co-authored-by: Taichi Gardener <taichigardener@gmail.com>

python/taichi/lang/matrix.py

@@ -227,6 +227,62 @@ def subscript(self, *indices):
                 j = 0
             return self(i, j)
 
+    @property
+    def x(self):
+        if impl.inside_kernel():
+            return self.subscript(0)
+        else:
+            return self[0]
+
+    @property
+    def y(self):
+        if impl.inside_kernel():
+            return self.subscript(1)
+        else:
+            return self[1]
+
+    @property
+    def z(self):
+        if impl.inside_kernel():
+            return self.subscript(2)
+        else:
+            return self[2]
+
+    @property
+    def w(self):
+        if impl.inside_kernel():
+            return self.subscript(3)
+        else:
+            return self[3]
+
+    @x.setter
+    def x(self, value):
+        if impl.inside_kernel():
+            self.subscript(0).assign(value)
+        else:
+            self[0] = value
+
+    @y.setter
+    def y(self, value):
+        if impl.inside_kernel():
+            self.subscript(1).assign(value)
+        else:
+            self[1] = value
+
+    @z.setter
+    def z(self, value):
+        if impl.inside_kernel():
+            self.subscript(2).assign(value)
+        else:
+            self[2] = value
+
+    @w.setter
+    def w(self, value):
+        if impl.inside_kernel():
+            self.subscript(3).assign(value)
+        else:
+            self[3] = value
+
     class Proxy:
         def __init__(self, mat, index):
             self.mat = mat
@@ -242,6 +298,38 @@ def __setitem__(self, key, value):
                 key = [key]
             self.mat(*key)[self.index] = value
 
+        @property
+        def x(self):
+            return self[0]
+
+        @property
+        def y(self):
+            return self[1]
+
+        @property
+        def z(self):
+            return self[2]
+
+        @property
+        def w(self):
+            return self[3]
+
+        @x.setter
+        def x(self, value):
+            self[0] = value
+
+        @y.setter
+        def y(self, value):
+            self[1] = value
+
+        @z.setter
+        def z(self, value):
+            self[2] = value
+
+        @w.setter
+        def w(self, value):
+            self[3] = value
+
     # host access
     def __getitem__(self, index):
         return Matrix.Proxy(self, index)

tests/python/test_linalg.py

@@ -339,3 +339,23 @@ def func():
     func()
     assert np.allclose(m.to_numpy()[1, 0, 0, :, :], np.array([[2, 4], [6, 8]]))
     assert np.allclose(v.to_numpy()[1, 0, 0, :], np.array([10, 12]))
+
+
+@ti.host_arch_only
+def test_vector_xyzw_accessor():
+    u = ti.Vector(2, dt=ti.i32, shape=(2, 2, 1))
+    v = ti.Vector(4, dt=ti.i32, shape=(2, 2, 1))
+
+    u[1, 0, 0].y = 3
+    v[1, 0, 0].w = 4
+
+    @ti.kernel
+    def func():
+        u[1, 0, 0].x = 8 * u[1, 0, 0].y
+        v[1, 0, 0].z = 1 - v[1, 0, 0].w
+        v[1, 0, 0].x = 6
+
+    func()
+    assert u[1, 0, 0].x == 24
+    assert u[1, 0, 0].y == 3
+    assert np.allclose(v.to_numpy()[1, 0, 0, :], np.array([6, 0, -3, 4]))