path: root/C++_from_the_Ground/Chapter_12(1).ipynb

{
 "metadata": {
  "name": "Chapter 12"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h1>Chapter 12: A Closer Look at Classes<h1>"
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.1, Page Number: 274<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Implementation of friend functions in python'''\n\nclass myclass:\n    __a=None\n    __b=None\n    def __init__(self,i,j):\n        self.__a=i\n        self.__b=j\n    def sum(self,x):   #Friend function\n        return sum1(x)\n        \ndef sum1(x):        \n    return x._myclass__a +x._myclass__b   #accessing private members\n\n#Variable declaration\nn=myclass(3,4)\n\n#Result\nprint n.sum(n)\n\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "7\n"
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.2, Page Number: 275<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Use a friend function'''\n\nclass c1:\n    __status=None\n    def set_status(self,state):\n        self.__status=state\n    \nclass c2:\n    __status=None\n    def set_status(self,state):\n        self.status=state\n    \n#Friend function    \ndef idle(a,b):\n    if a._c1__status or b._c2__status :\n        return 0\n    else:\n        return 1\n    \n#variable declarations\ndef IDLE():             #Constants\n    return 0\ndef INUSE():\n    return 1\nx=c1()\ny=c2()\n\nx.set_status(IDLE())\ny.set_status(IDLE())\n\nif idle(x,y):\n    print \"Screen Can Be Used.\"\n    \nx.set_status(INUSE())\n\nif idle(x,y):\n    print \"Screen Can Be Used.\"\nelse:\n    print \"Pop-up In Use.\"\n    \n    ",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Screen Can Be Used.\nPop-up In Use.\n"
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.3, Page Number: 277<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''A function can be member of one class and a friend of another'''\n\n #Constants\ndef IDLE():            \n    return 0\ndef INUSE():\n    return 1\n\nclass c1:\n    __status=None\n    def set_status(self,state):\n        self.__status=state\n    def idle(self,b):            #now a member of c1\n        if self.__status or b._c2__status :\n            return 0\n        else:\n            return 1\n    \nclass c2:\n    __status=None     #IDLE if off INUSE if on screen\n    def set_status(self,state):\n        self.status=state\n        \n#Variable declarations        \nx=c1()\ny=c2()\n\nx.set_status(IDLE())\ny.set_status(IDLE())\n\nif idle(x,y):\n    print \"Screen Can Be Used.\"\n    \nx.set_status(INUSE())\n\nif idle(x,y):\n    print \"Screen Can Be Used.\"\nelse:\n    print \"Pop-up In Use.\"\n        ",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Screen Can Be Used.\nPop-up In Use.\n"
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.4, Page Number: 278<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Use of overloaded constructors'''\n#Printing the time passed since the functon started instead of ringing the bell.\n\nimport time,string\n\nclass timer:\n    __seconds=None\n    \n    def __init__(self,t1,t2=None):\n        if t2==None:\n            if isinstance(t1,int):   #seconds specified as an integer\n                self.__seconds=t1\n            else:                    #seconds specified as a string\n                self.__seconds=string.atoi(t1)\n        else:                        #time in minutes and seconds\n            self.__seconds=t1*60+t2\n            \n    def run(self):\n        t1=time.clock()\n        while (time.clock()-t1)<self.__seconds:\n            a=10\n        print time.clock()-t1\n \n        \na=timer(10)\nb=timer(\"20\")\nc=timer(1,10)\na.run()            #count 10 seconds\nb.run()            #count 20 seconds\nc.run()            #count 1 minute,10 seconds\n        ",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "10.0000009774\n20.0000009774"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "\n70.0000004887"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "\n"
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.5, Page Number: 280<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Demonstarate dynamic initialization'''\n#Printing the time passed since the functon started instead of ringing the bell.\n\nimport time,string\n\nclass timer:\n    __seconds=None\n    \n    def __init__(self,t1,t2=None):\n        if t2==None:\n            if isinstance(t1,int):   #seconds specified as an integer\n                self.__seconds=t1\n            else:                    #seconds specified as a string\n                self.__seconds=string.atoi(t1)\n        else:                        #time in minutes and seconds\n            self.__seconds=t1*60+t2\n            \n    def run(self):\n        t1=time.clock()\n        while (time.clock()-t1)<self.__seconds:\n            a=10\n        print time.clock()-t1\n            \na=timer(10)\na.run()\n\nprint \"Enter number of seconds: \"\nstr=\"20\"\nb=timer(str)                       #initialize at the run time\nc.run()\n\nprint \"Enter minutes and seconds: \"\nmin=1\nsec=10\nc=timer(min,sec)                   #initialize at the run time\nc.run()\n        ",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "10.0000004887\nEnter number of seconds: \n70.0000009774"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "\nEnter minutes and seconds: \n70.0000009774"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "\n"
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.6, Page Number: 282<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Demonstrate object assignment'''\n\nclass myclass:\n    __a=None             #private members\n    __b=None\n    def setab(self,i,j): #publc functons\n        self.__a=i\n        self.__b=j\n    def showab(self):\n        print \"a is \",self.__a\n        print \"b is \",self.__b\n\n#Variable declaration\nob1 = myclass()\nob2 = myclass()\n\n#Intalizing\nob1.setab(10,20)\nob2.setab(0,0)\n\nprint \"ob1 before assignment: \"\nob1.showab()\nprint \"ob2 before assignment: \"\nob2.showab()\n\nob2 = ob1            #assign ob1 to ob2\n\n#Result\nprint \"ob1 after assignment: \"\nob1.showab()\nprint \"ob2 after assignment: \"\nob2.showab()\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "ob1 before assignment: \na is  10\nb is  20\nob2 before assignment: \na is  0\nb is  0\nob1 after assignment: \na is  10\nb is  20\nob2 after assignment: \na is  10\nb is  20\n"
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.7, Page Number: 283<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Demonstration of passing objects to functions'''\n'''Implementing call by value method in python'''\n\nfrom copy import deepcopy\n        \nclass OBJ:\n    def set_i(self,x):\n        self.__i=x\n    def out_i(self):\n        print self.__i,\n    \ndef f(x):\n    x=deepcopy(x)\n    x.out_i()     #outputs 10\n    x.set_i(100)  #this affects only local copy\n    x.out_i()     #outputs 100\n    \n#Variable declaration\no=OBJ()\no.set_i(10)\nf(o)               \no.out_i()         #still outputs 10, value of i unchanged\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "10 100 10\n"
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.8, Page Number: 284<h3> "
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Constructors, destructors, and passing objects'''\n\nclass myclass:                       \n    def __init__(self,i):\n        self.__val=i\n        print \"Constructing\"\n    def __del__(self):\n        print \"Destructing\"\n    def getval(self):\n        return self.__val\n        \ndef display(ob):\n    print ob.getval()\n\n#Varable declaration\na=myclass(10)\n\ndisplay(a)\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Constructing\nDestructing\n10\n"
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.9, Page Number: 286<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Passing objects with a pointer'''\n#The problem shown in C++, will not occur in python because it does not have pointers.\n\nfrom ctypes import *\n\nclass myclass:\n    def __init__(self,i):\n        print \"Allocating p\"\n        self.p=pointer(c_int(i))\n    def __del__(self):\n        print \"Freeing p\"\n    def getval(self):\n        return self.p[0]\n        \ndef display(ob):\n    print ob.getval()\n\n#Variable declaration\na=myclass(10)\n\ndisplay(a)\n    ",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Allocating p\n10\n"
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.10, Page Number: 287<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Passing objects by reference'''\n\nfrom ctypes import *\nclass myclass:\n    def __init__(self,i):\n        print \"Allocating p\"\n        self.p=pointer(c_int(i))\n    def __del__(self):\n        print \"Freeing p\"\n    def getval(self):\n        return self.p[0]\n        \ndef display(ob):\n    print ob[0].getval()\n\n#Variable declaration\na=[]\na.append(myclass(10))\n\ndisplay(a)\n    ",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Freeing p\nAllocating p\n10\n"
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.11, Page Number: 288<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Returning an object'''\n\nclass sample:\n    __s=None\n    def show(self):\n        print self.__s\n    def set(self,str):\n        self.__s=str\n\n#Return an object of type sample\ndef input():\n    str=sample()\n    instr = \"Hello\"       #User input\n    str.set(instr)\n    return str\n\n#Variable declaration\nob=sample()\n\n#assign returned object to ob\nob=input()\n\n#Result\nob.show()\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Hello\n"
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.12, Page Number: 289<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Returning an object'''\n#The error shown in C++ doesnt occur here.\nclass sample:\n    __s=None\n    def __init__(self):\n        self.__s=0\n    def __del__(self):          \n        print \"Freeing p\"\n    def show(self):\n        print self.__s\n    def set(self,str):\n        self.__s=str\n        \n#This function takes one object parameter\ndef input():\n    str=sample()\n    instr=\"Hello\"    #User input\n    str.set(instr)\n    return str\n\n#Variable declaration\nob=sample()\n\n#assign returned object to ob\nob=input()\n\n#Result\nob.show()\n\n\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Freeing p\nFreeing p\nHello\n"
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.13, Page Number: 292<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Implementing a copy constructor'''\n#Copy construcor doesnt work in this example, it works only when explicitly called\n\nclass myclass:\n    __p=None\n    def __init__(self,i):\n        if isinstance(i,int):\n            print \"Allocating p\"\n            self.__p=i\n        else:\n            print \"Copy constructor called\"\n            self.__p=i.getval()\n    def __del__(self):          \n        print \"Freeing p\"\n    def getval(self):\n        return self.__p\n        \n#This function takes one object parameter\ndef display(ob):\n    print ob.getval()\n\n#Variable declaration\nob=myclass(10)\n\n#Result\ndisplay(ob)\n\n\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Allocating p\n10\n"
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.14, Page Number: 294<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Implementing a copy constructor'''\n\n\nclass myclass:\n    __p=None\n    def __init__(self,i):\n        if isinstance(i,int):\n            print \"Allocating p\"\n            self.__p=i\n        else:\n            print \"Copy constructor called\"\n            self.__p=i.getval()\n    def __del__(self):          \n        print \"Freeing p\"\n    def getval(self):\n        return self.__p\n        \n\n#Variable declaration\na=myclass(10)         #calls normal constructor\nb=myclass(a)           #calls copy constructor\n\n\n\n\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Allocating p\nCopy constructor called\n"
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.15, Page Number: 295<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Implementing a copy constructor'''\n\n\nclass myclass:\n    def __init__(self,i=0):\n        if isinstance(i,int):\n            print \"Normal constructor\"\n        else:\n            print \"Copy constructor\"\n\n\n#Variable declaration\na=myclass()           #calls normal constructor\n\nf=myclass()\na=myclass(f)          #Invoke copyconstructor\n\n\n\n\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Normal constructor\nNormal constructor\nCopy constructor\n"
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": "<h3>Example 12.16, Page Number: 297<h3>"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "'''Implementation of the this pointer'''\n#Here self works as this\n\nclass c1:\n    def __init__(self):\n        self.__i=None\n    def load_i(self,val):\n        self.__i=val\n    def get_i(self):\n        return self.__i\n    \n#Variable declaration    \no=c1()\n\no.load_i(100)\n\n#Result\nprint o.get_i()\n",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "100\n"
      }
     ],
     "prompt_number": 13
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "",
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}