#!/usr/bin/env python

# Written by: DGC

#==============================================================================

class Line(object):

""" A non-directed line. """

def __init__(self, point_1, point_2):

self.point_1 = point_1

self.point_2 = point_2

def __eq__(self, line):

""" Magic method to overide == operator. """

# if the lines are equal then the two points must be the same, but not

# necessarily named the same i.e self.point_1 == line.point_2 and

# self.point_2 == line.point_1 means that the lines are equal.

if (type(line) != Line):

return False

if (self.point_1 == line.point_1):

# line numbering matches

return self.point_2 == line.point_2

elif (self.point_1 == line.point_2):

# line numbering does not match

return self.point_2 == line.point_1

else:

# self.point_1 is not the start or end of the other line, not equal

return False

#==============================================================================

class Vector(object):

""" A directional vector. """

def __init__(self, x, y):

self.x = x

self.y = y

def __eq__(self, vector):

""" Magic method to overide == operator. """

if (type(vector) != Vector):

return False

return (self.x == vector.x) and (self.y == vector.y)

#------------------------------------------------------------------------------

# Factory functions

#------------------------------------------------------------------------------

class Factory(object):

@classmethod

def line_from_point_vector(self, point, vector):

""" Returns the line from travelling vector from point. """

new_point = (point[0] + vector.x, point[1] + vector.y)

return Line(point, new_point)

@classmethod

def vector_from_line(self, line):

"""

Returns the directional vector of the line. This is a vector v, such

that line.point_1 + v == line.point_2

"""

return Vector(

line.point_2.x - line.point_1.x,

line.point_2.y - line.point_1.y

)

#==============================================================================

if (__name__ == "__main__"):

# make a line from (1, 1) to (1, 0), check that the line made from the

# point (1, 1) and the vector (0, -1) is the same line.

constructor_line = Line((1, 1), (1, 0))

vector = Vector(0, -1);

factory_line = Factory.line_from_point_vector(

(1, 1),

vector

)

print(constructor_line == factory_line)