CSC352 StrangeShape.py

--D. Thiebaut 20:53, 24 February 2010 (UTC)

---

#! /usr/bin/python
# strangeSurface.py
# D. Thiebaut
#
import random
import math
import pickle

class Point:
    """A simple container for the x & y coordinates of a point"""
    def __init__(self, h, v):
        self.h = h
        self.v = v

class StrangeShape:
    """The strange shape we need to measure the area of.  
    The main function is isInside( point ) which returns True
    if the point is inside the surface, False otherwise."""

    def __init__( self ):
        """constructor: generate the polygone"""
        self.polygon = self.generateStrangePoly()

    def generateStrangePoly( self ):
            return pickle.loads("""(lp0
(F0.10000000000000001
F0.10000000000000001
tp1
a(F0.90000000000000002
F0.10000000000000001
tp2
a(F0.5
F0.20000000000000001
tp3
a(F0.90000000000000002
F0.5
tp4
a(F0.90000000000000002
F0.90000000000000002
tp5
a(F0.10000000000000001
F0.90000000000000002
tp6
a.
""")
        
    def Angle2D(self, x1, y1, x2, y2):
        """utility function"""
        theta1 = math.atan2(y1, x1)
        theta2 = math.atan2(y2, x2)
        dtheta = theta2 - theta1
        while dtheta > math.pi:
                dtheta -= 2.0 * math.pi
        while dtheta < -math.pi:
                dtheta += 2.0 * math.pi
        return dtheta

    def isInside( self, p ):
        """the test function.  Returns True if point inside surface"""
        angle = 0.0
        n = len(self.polygon)
 
        for i, (h, v) in enumerate( self.polygon ):
                p1 = Point(h - p.h, v - p.v)
                h, v = self.polygon[(i + 1) % n]
                p2 = Point(h - p.h, v - p.v)
                angle += self.Angle2D(p1.h, p1.v, p2.h, p2.v);
 
        if abs(angle) < math.pi:
                return False
        return True


# ----------------------------------------------------------------------------
def main():
    shape = StrangeShape()
    while True:
        print "enter a point's coordinates: "
        p = Point( input( "x> " ), input( "y> " ) )
        if shape.isInside( p ):
            print "+ Point is inside"
        else:
            print "- Point is outside"
        
        
main()