add the vector

Author: zingale

test_vector.py

@@ -0,0 +1,8 @@
+import vector
+
+
+def test_add():
+    v1 = vector.Vector(1, 2)
+    v2 = vector.Vector(2, 3)
+
+    assert v1 + v2 == vector.Vector(3, 5)

vector.py

@@ -0,0 +1,69 @@
+import math
+
+
+class Vector:
+    """ a general two-dimensional vector """
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def __eq__(self, other):
+        return self.x == other.x and self.y == other.y
+
+    def __str__(self):
+        return f"({self.x} î + {self.y} ĵ)"
+
+    def __repr__(self):
+        return f"Vector({self.x}, {self.y})"
+
+    def __add__(self, other):
+        if isinstance(other, Vector):
+            return Vector(self.x + other.x, self.y + other.y)
+        else:
+            # it doesn't make sense to add anything but two vectors
+            print(f"we don't know how to add a {type(other)} to a Vector")
+            raise NotImplementedError
+
+    def __sub__(self, other):
+        if isinstance(other, Vector):
+            return Vector(self.x - other.x, self.y - other.y)
+        else:
+            # it doesn't make sense to add anything but two vectors
+            print(f"we don't know how to add a {type(other)} to a Vector")
+            raise NotImplementedError
+
+    def __mul__(self, other):
+        if isinstance(other, int) or isinstance(other, float):
+            # scalar multiplication changes the magnitude
+            return Vector(other*self.x, other*self.y)
+        else:
+            print("we don't know how to multiply two Vectors")
+            raise NotImplementedError
+
+    def __matmul__(self, other):
+        # a dot product
+        if isinstance(other, Vector):
+            return self.x*other.x + self.y*other.y
+        else:
+            print("matrix multiplication not defined")
+            raise NotImplementedError
+
+    def __rmul__(self, other):
+        return self.__mul__(other)
+
+    def __truediv__(self, other):
+        # we only know how to multiply by a scalar
+        if isinstance(other, int) or isinstance(other, float):
+            return Vector(self.x/other, self.y/other)
+
+    def __abs__(self):
+        return math.sqrt(self.x**2 + self.y**2)
+
+    def __neg__(self):
+        return Vector(-self.x, -self.y)
+
+    def cross(self, other):
+        # a vector cross product -- we return the magnitude, since it will
+        # be in the z-direction, but we are only 2-d
+        return abs(self.x*other.y - self.y*other.x)