1 # Copyright (c) 2013 The Chromium OS Authors. All rights reserved. 2 # Use of this source code is governed by a BSD-style license that can be 3 # found in the LICENSE file. 4 5 """This is a simple geometry module containing basic elements.""" 6 7 8 # To allow roundoff error 9 TOLERANCE = 0.00000001 10 11 12 def about_eq(f1, f2): 13 """Determine if two numbers are about equal within the TOLERANCE. 14 15 @param f1: float number 1 16 @param f2: float number 2 17 """ 18 return abs(f1 - f2) < TOLERANCE 19 20 21 class Point: 22 """A point class.""" 23 def __init__(self, x=None, y=None): 24 """Initialize a point. 25 26 @param x: x coordinate 27 @param y: y coordinate 28 """ 29 self.x = x if x is None else float(x) 30 self.y = y if y is None else float(y) 31 32 def __bool__(self): 33 """A boolean indicating if this point is defined.""" 34 return self.x is not None and self.y is not None 35 36 def __eq__(self, p): 37 """Determine if this point is equal to the specified point, p. 38 39 @param p: a point 40 """ 41 return about_eq(self.x, p.x) and about_eq(self.y, p.y) 42 43 def __hash__(self): 44 """Redefine the hash function to meet the consistency requirement. 45 46 In order to put an item into a set, it needs to be hashable. 47 To make an object hashable, it must meet the consistency requirement: 48 a == b must imply hash(a) == hash(b) 49 """ 50 return hash((self.x, self.y)) 51 52 def __str__(self): 53 """The string representation of the point value.""" 54 return 'Point: (%.4f, %.4f)' % (self.x, self.y) 55 56 def distance(self, p): 57 """Calculate the distance between p and this point. 58 59 @param p: a point 60 """ 61 dist_x = p.x - self.x 62 dist_y = p.y - self.y 63 return (dist_x ** 2 + dist_y ** 2 ) ** 0.5 64 65 def value(self): 66 """Return the point coordinates.""" 67 return (self.x, self.y) 68 69 # __bool__ is used in Python 3.x and __nonzero__ in Python 2.x 70 __nonzero__ = __bool__ 71 72 73 class Circle: 74 """A circle class.""" 75 def __init__(self, center, radius): 76 """Initialize a circle. 77 78 @param center: the center point of the circle 79 @param radius: the radius of the circle 80 """ 81 self.center = center 82 self.radius = radius 83 84 def __bool__(self): 85 """A boolean indicating if this circle is defined.""" 86 return self.center is not None and self.radius is not None 87 88 def __contains__(self, p): 89 """Determine if p is enclosed in the circle. 90 91 @param p: a point 92 """ 93 return self.center.distance(p) <= self.radius + TOLERANCE 94 95 def __eq__(self, c): 96 """Determine if this circle is equal to the specified circle, c. 97 98 @param c: a circle 99 """ 100 return self.center == c.center and about_eq(self.radius, c.radius) 101 102 def __hash__(self): 103 """Redefine the hash function to meet the consistency requirement. 104 105 In order to put an item into a sets.Set, it needs to be hashable. 106 To make an object hashable, it must meet the consistency requirement: 107 a == b must imply hash(a) == hash(b) 108 """ 109 return hash((self.center, self.radius)) 110 111 def __str__(self): 112 """The string representation of the circle value.""" 113 return ('Center: %s, %s' % (str(self.center), 114 'Radius: %.4f' % self.radius) 115 if self else 'Circle is None') 116 117 # __bool__ is used in Python 3.x and __nonzero__ in Python 2.x 118 __nonzero__ = __bool__ 119
