updated contents from Atlas repo

operator/vector.py

@@ -0,0 +1,140 @@
+"""
+
+The `+` operator produces a `Vector` result.
+
+    >>> v1 = Vector(2, 4)
+    >>> v2 = Vector(2, 1)
+    >>> v1 + v2
+    Vector(4, 5)
+
+We can also implemement the `*` operator to perform scalar multiplication
+or elementwise multiplication.
+
+    >>> v = Vector(3, 4)
+    >>> abs(v)
+    5.0
+    >>> v * 3
+    Vector(9, 12)
+    >>> abs(v * 3)
+    15.0
+    >>> v25 = Vector(2, 5)
+    >>> v71 = Vector(7, 1)
+    >>> v71 * v25
+    Vector(14, 5)
+
+A vector can be used in a boolean context, where it will be considered
+_falsy_ if it has magnitude zero, otherwise it is _truthy_::
+
+    >>> bool(v)
+    True
+    >>> bool(Vector(0, 0))
+    False
+
+Vectors can have n-dimensions::
+
+    >>> v3 = Vector(1, 2, 3)
+    >>> len(v3)
+    3
+    >>> v3
+    Vector(1, 2, 3)
+    >>> abs(v3)  # doctest:+ELLIPSIS
+    3.74165738...
+    >>> v3 + Vector(4, 5, 6)
+    Vector(5, 7, 9)
+    >>> v3 * 5
+    Vector(5, 10, 15)
+    >>> v2 + v3
+    Traceback (most recent call last):
+      ...
+    ValueError: Addition applies only to vectors of equal dimensions.
+
+
+The `repr` of a Vector is produced with the help of the `reprlib.repr`
+function, limiting the size of the output string:
+
+    >>> Vector(*range(100))
+    Vector(0, 1, 2, 3, 4, 5, ...)
+
+
+Dot product is a scalar: the sum of the products of the corresponding
+components of two vectors.
+
+    >>> v25 = Vector(2, 5)
+    >>> v71 = Vector(7, 1)
+    >>> v25.dot(v71)
+    19
+    >>> Vector(1, 2, 3).dot(Vector(4, 5, 6))
+    32
+    >>> Vector(1, 2, 3).dot(Vector(-2, 0, 5))
+    13
+
+
+As described in PEP 465, starting with Python 3.5, `__matmul__` is
+the special method for the new ``@`` operator, to be used the dot
+product of vectors or matrix multiplication (as opposed to ``*``
+which is intended for scalar or elementwise multiplication):
+
+    >>> # skip these tests on Python < 3.5
+    >>> v25 @ v71  # doctest:+SKIP
+    19
+    >>> v71 * v25
+    Vector(14, 5)
+    >>> Vector(1, 2, 3) @ Vector(-2, 0, 5)    # doctest:+SKIP
+    13
+
+"""
+
+# BEGIN VECTOR_OPS
+import math
+import numbers
+import reprlib
+
+EQ_DIMENSIONS_MSG = '%s applies only to vectors of equal dimensions.'
+
+class Vector:
+    """An n-dimensional vector"""
+
+    def __init__(self, *components):  # <1>
+        self._components = tuple(components)  # <2>
+
+    def __repr__(self):
+        return 'Vector' + (reprlib.repr(self._components))  # <3>
+
+    def __iter__(self):
+        return iter(self._components)  # <4>
+
+    def __abs__(self):
+        return math.sqrt(sum(comp*comp for comp in self)) # <5>
+
+    def __len__(self):
+        return len(self._components)  # <6>
+
+    def __add__(self, other):
+        if len(self) != len(other):
+            raise ValueError(EQ_DIMENSIONS_MSG % 'Addition')
+        return Vector(*(a+b for a, b in zip(self, other)))  # <7>
+
+    def __mul__(self, other):
+        if isinstance(other, numbers.Number):
+            return Vector(*(comp*other for comp in self))  # <8>
+        else:
+            return self.elementwise_mul(other)  # <9>
+
+    def elementwise_mul(self, other):
+        if len(self) != len(other):
+            raise ValueError(EQ_DIMENSIONS_MSG %
+                             'Elementwise multiplication')
+        return Vector(*(a*b for a, b in zip(self, other)))  # <10>
+
+    def __bool__(self):
+        return any(self)  # <11>
+
+    def dot(self, other):
+        if len(self) != len(other):
+            raise ValueError(EQ_DIMENSIONS_MSG %
+                             'Dot product')
+        return sum(a*b for a, b in zip(self, other))  # <12>
+
+    __matmul__ = dot  # support @ operator in Python 3.5
+
+# END VECTOR_OPS