"""
A 2-dimensional vector class

    >>> v1 = Vector2d(3, 4)
    >>> print(v1.x, v1.y)
    3.0 4.0
    >>> x, y = v1
    >>> x, y
    (3.0, 4.0)
    >>> v1
    Vector2d(3.0, 4.0)
    >>> v1_clone = eval(repr(v1))
    >>> v1 == v1_clone
    True
    >>> print(v1)
    (3.0, 4.0)
    >>> octets = bytes(v1)
    >>> octets
    b'd\\x00\\x00\\x00\\x00\\x00\\x00\\x08@\\x00\\x00\\x00\\x00\\x00\\x00\\x10@'
    >>> abs(v1)
    5.0
    >>> bool(v1), bool(Vector2d(0, 0))
    (True, False)


Test of ``.frombytes()`` class method:

    >>> v1_clone = Vector2d.frombytes(bytes(v1))
    >>> v1_clone
    Vector2d(3.0, 4.0)
    >>> v1 == v1_clone
    True

"""

from array import array
import math


class Vector2d:
    typecode = 'd'

    def __init__(self, x, y):
        self.x = float(x)
        self.y = float(y)

    def __iter__(self):
        return (i for i in (self.x, self.y))

    def __repr__(self):
        class_name = type(self).__name__
        return '{}({!r}, {!r})'.format(class_name, *self)

    def __str__(self):
        return str(tuple(self))

    def __bytes__(self):
        return (bytes([ord(self.typecode)]) +
                bytes(array(self.typecode, self)))

    def __eq__(self, other):
        return tuple(self) == tuple(other)

    def __abs__(self):
        return math.hypot(self.x, self.y)

    def __bool__(self):
        return bool(abs(self))

# tag::VECTOR2D_V1[]
    @classmethod  # <1>
    def frombytes(cls, octets):  # <2>
        typecode = chr(octets[0])  # <3>
        memv = memoryview(octets[1:]).cast(typecode)  # <4>
        return cls(*memv)  # <5>
# end::VECTOR2D_V1[]