{
 "metadata": {
  "name": ""
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import math"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "class Quadratic :\n",
      "    \"\"\"Codes a class for quadratic polynomials.\n",
      "    Attributes (class variables) :\n",
      "    a, b, c : coefficients of ax^2 + bx + c.\n",
      "    Methods (class functions) :\n",
      "    roots() : returns a tuple containing the roots\n",
      "    __call__(x) : returns the value of the poly at x.\n",
      "    display() : displays the equation.\n",
      "    \"\"\"\n",
      "    \n",
      "    def __init__(self, a, b, c) :\n",
      "        self.a = a\n",
      "        self.b = b\n",
      "        self.c = c\n",
      "        \n",
      "    def __call__(self, x) :\n",
      "        return self.a *x*x + self.b *x + self.c\n",
      "        \n",
      "    def roots(self) :\n",
      "        a = self.a\n",
      "        b = self.b\n",
      "        c = self.c\n",
      "        \n",
      "        if a == 0 :\n",
      "            if b == 0 :\n",
      "                print \"Constant = 0\"\n",
      "                rval = None\n",
      "            else :\n",
      "                rval = - float(c)/b\n",
      "        else :\n",
      "            if b*b - 4*a*c < 0 :\n",
      "                print \"Complex roots.\"\n",
      "                rval = None\n",
      "            else :\n",
      "                x1 = (-b + math.sqrt(b*b - 4*a*c))/(2*a)\n",
      "                x2 = (-b - math.sqrt(b*b - 4*a*c))/(2*a)\n",
      "                rval = (x1, x2)\n",
      "        return rval\n",
      "    \n",
      "    def __str__(self) :\n",
      "        return \"%g x^2 + %g x + %g\" %(self.a, self.b, self.c)\n",
      "    def __repr__(self) :\n",
      "        return self.__str__()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "q = Quadratic(4, 4, 1)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "if __name__ == '__main__' :\n",
      "    print q.roots()\n",
      "    print q(1)\n",
      "    print q"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "(-0.5, -0.5)\n",
        "9\n",
        "4 x^2 + 4 x + 1\n"
       ]
      }
     ],
     "prompt_number": 4
    }
   ],
   "metadata": {}
  }
 ]
}