Thursday 12/1 online class

We are going to review the Chapter 14 using the following class material:

1. Video Clip on the Recursion of Chapter 14: http://www.youtube.com/watch?v=qyaVrP8y0RM
You may view this video in full screen HD (720) 

• "countDown.cpp", the example program in textbook Chap14-2 
• wikipedia on Call Stack

2. Audio Clips (reside in Course Outline) on Chapter 14 by Prof. Burns.

Recursion Examples

http://www.dcs.bbk.ac.uk/~roger/cpp/week16.htm

Chap12.3 sample code

#include <fstream>
#include <iomanip>
#include <iostream>
#include <string>
using namespace std;

struct Student
{
  string name;
  int id;
  float gpa;
};
 
void printStudents(Student* student, int nStudents)
{
  int i;
  for (i = 0; i < nStudents; i++)
  {
    cout << "Name = " << left << setw(30) << student[i].name;
    cout.fill('0'); 
    cout << " ID = " << right << setw(7)
      << student[i].id << ", gpa = "
      << student[i].gpa << endl;
    cout.fill(' '); 
  }
}

int main()
{
  // open a file for input
  ifstream fin;
  fin.open("students.txt");
  if (!fin.good()) throw "I/O error";
 
  // create an empty list
  const int MAX_STUDENTS = 100; // capacity
  int nStudents = 0; // initially empty
  Student student[MAX_STUDENTS];
 
  // read and save the records
  while (fin.good())
  {
    // create a record and read it from file
    Student aStudent;
    getline(fin, aStudent.name);

    fin >> aStudent.id;
    fin.ignore(1000, 10);
 
    fin >> aStudent.gpa;
    fin.ignore(1000, 10);
 
    fin.ignore(1000, 10); // skip the ---------- separator

    // add record to list, if it's not full
    if (nStudents < MAX_STUDENTS)
      student[nStudents++] = aStudent;
  }
  fin.close();
 
  // sort the students by name
  for (int i = 0; i < nStudents; i++)
  {
    for (int j = i + 1; j < nStudents; j++)
    {
      if (student[i].name > student[j].name)
      {
        Student temp = student[i];
        student[i] = student[j];
        student[j] = temp;
      }
    }
  }

  printStudents(student, nStudents);
 
  return 0;
} // main

Pointer Example 1

#include <iostream>
#include <string>
using namespace std;

int main()
{

  int andy = 25;
  int fred = andy;
  int* ted = &andy;
  cout << andy << endl;
  cout << fred << endl;
  cout << *ted << endl;
  cout << ted << endl;

    // declare the variables:

    int nNumber;
    int *pPointer;

    // now, give a value to them:

    nNumber = 15;
    pPointer = &nNumber;

    cout << "nNumber is equal to :" << nNumber << endl;
    *pPointer = 25;

    cout << "nNumber is equal to :" << nNumber << endl;
  return 0;
}

Array of Struct Initialization

#include <iostream>
#include <string>
using namespace std;


// A struct Definition
struct Student
{
  string name;
  int id;
  float gpa;
}; // Student

int main()
{
  Student a[2]={{"Tom",123455, 3.66},
                {"Tom",123455, 3.66}};
  a[0].name = "George Washington";
  a[0].gpa = 3.14;
  a[0].id = 123456;

  cout << "Name=" << a[0].name
       << ", ID=" << a[0].id
       << ", GPA=" << a[0].gpa << endl;

  cout << "Name=" << a[1].name
       << ", ID=" << a[1].id
       << ", GPA=" << a[1].gpa << endl;

  return 0;
}

Passing Struct to Function

#include <iostream>
#include <string>
using namespace std;

struct Student
{
  string name;
  int id;
  float gpa;
}; // Student

Student getGeorge()
{
  Student george;
  george.name = "George";
  george.id = 123456;
  george.gpa = 3.4;
  return george;
} // getGeorge

void printRecord(Student&amp; x)
{
  cout &lt;&lt; "Name=" &lt;&lt; x.name;
  cout &lt;&lt; ", ID=" &lt;&lt; x.id;
  cout &lt;&lt; ", GPA=" &lt;&lt; x.gpa;
} // printRecord

int main()
{
  Student s = getGeorge();
  printRecord(s);
  return 0;
} // main

Passing Array to Function

#include
#include
using namespace std;

double getAverage(int* score, int n)
{
  int sum = 0;
  int i = 0;
  for (i = 0; i &lt; n; i++)
    sum += score[i];
  double average = double(sum) / n;
  return average;
} // getAverage

int main()
{
  int daysPerMonth[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  cout &lt;&lt; "Average = " &lt;&lt; getAverage(daysPerMonth, 12) &lt;&lt; endl;
  return 0;
} // main

Struct Sample Code

#include <string>
#include <iostream>
using namespace std;

  struct Course
  {
    string name;
    int session;
    float grade;
    string prereq;
    string teacher;
  }; // Student

int main()
{
/* how to demarc the structs and arrays
 * struc s[5] = { {s1, s2, s3, s4, s5},
 *                {s1, s2, s3, s4, s5},
 *                 ....}};
 */
  Course clist[5] = {
   {"COMSC110", 3131, 100.00, "COMSC100","Robert"},
   {"COMSC100", 1111, 100.00, "COMSC90","Tony"},
   {"COMSC110", 2131, 100.00, "COMSC100","Larry"},
   {"COMSC265", 3331, 100.00, "COMSC110","Joe"},
   {"COMSC110", 3431, 100.00, "COMSC100","Tom"}};
//  clist[0].session = 3131;
//  clist[0].teacher = "Tony";
//  clist[0].name = "COMSC110";

  string term;
  cout << "What Course are you looking for? ";
  getline(cin, term);

  // a way to querry the course, and print out only COMSC110
  for(int i =0; i <5; i++)
    if(clist[i].name == term)
    cout << clist[i].name << ": "
       << clist[i].session << " by "
       << clist[i].teacher << endl;

  return 0;
}

Testing Scopes

#include <iostream>
using namespace std;

int main()
{
  int j = 1;
  cout << j << endl;

  // assigning the address of outer j to jptr
  int* jptr = &j;

  // creating j2ptr to hold the address of inner j
  int* j2ptr;
  cout << jptr
       << "____________________"  << endl;
  int i = 5;
  for (int j = 1; j<i ; j++)
  {
    // this for loop only operates on the
    // inner j
    j2ptr = &j;
    cout << "Rock and Roll!" << j << endl;
  }

  // the outer j is not affected by the
  // above for loop
  cout << j2ptr
       << "____________________"  << endl;
  cout << j << endl;
  return 0;
}

Pointers Reference

pointers explained
pointer examples

Tesing Array

#include <iostream>
using namespace std;

void enterArray(int* a, int size)
{
  // read and save in the array according the the size
  int i;
  for (i = 0; i < size; i++)
  {
    cout << "element " << i+1 << ": ";
    cin >> a[i];
  } // for

  // print out the content
  for (i = 0; i < size; i++)
    cout << a[i] << ' ';
  cout << endl;
}

int main()
{
  int size;
  while (size)
  {
    int* intPtr; // a pointer to the integer type
    cout << endl
         << "What is the size of the array: (0 to quit) ";
    cin >> size;
    int* score = new int[size];
    intPtr = score;
    cout << "array address: "<< *score << endl;

    enterArray(score, size);
    cout << "the pointed items: ";
    for (int i=0; i<size+4; i++)
      cout << *intPtr++ << ' ';
    delete [] score;
  }

  return 0;
} // main

Sorting References

animation
wiki
quick sort
quick sort animation

floating point data references

float internal 

float wiki 
float converter

floating point data representation

//
// This program is an illustration for potential floating point boundary error
// only the floating point number > 1 case is implemented.
#include <fstream>
#include <iostream>
#include <string>
using namespace std;

int main()
{
  ofstream fout;
  fout.open("data.txt");
  if (!fout.good()) throw "I/O error";

  double x, mant;
  int exp = 0;
  cout << "Enter a postive x > 1: ";

  //Now find exponent and mantissa
  cin >> x;
  cin.ignore(1000,10);
  fout << x << endl;

  //
  // shifting the decimal point left
  // until the number is smaller than 1
  // to obtain the exponent
  mant = x;
  while (mant >= 1)
  {
    mant /= 2;
    exp++; // At this point x = mant * 2^(exp)
  }
  while (mant < 0.5)
  {
    mant *= 2;
    exp--;
  }
  cout << x <<" is stored in exponent and mantisa, \n"
       << "as 2^(eee) *.mmm\n"
       << x <<" = ";
  cout << "2^(" <<exp<<") *.";
  fout << x <<" is stored as mmm.mmm\n"
       << x <<" = ";
  //
  // shifting the decimal point right
  // to convert decimal fraction to binary mantisa
  int i=0;
  string s = "";   // mantisa
  string ss = "";  // binary float
  float bfrac = 0; // binary fraction
  float weight = 1;      // fraction bit weight
  while (mant > 0)
  {
    mant *= 2;
    if (mant >= 1)
    {
      s = s + '1';
      ss = ss + '1';
      mant -= 1;
      if(i >= exp) bfrac += weight = weight/2;
    }
    else
    {
      s = s + '0';
      ss = ss + '0';
      if(i >= exp) weight = weight/2;
    }
    if(++i == exp) ss = ss + '.';
    if(i >= 23) break;
  }
  cout << s << endl;
  cout << "or, presented as: " << ss << endl;
  fout << ss << endl;

  cout << "regenerated decimal fraction from binary fraction: \n"
       << bfrac << endl;
  fout << "regenerated decimal fraction from binary fraction: \n"
       << bfrac << endl;
  return 0;
}

floating point data range and precision

#include <iomanip>
#include <iostream>
using namespace std;

int main()
{
  cout << fixed << setprecision(25) << endl;
  cout << "--------- round-off error------------" << endl;
  double x = 3;
  cout << x << endl;
  cout << (x + 0.0000000000000001) << endl;
  cout << (x + 0.000000000000001) << endl << endl;

  cout << "--------- more round-off -------------" << endl;
  cout << scientific << setprecision(25) << endl;
  double d;
  for (d = 0; d != 2.0; d += 0.4)
    cout << d << endl;
  cout << d << endl << endl;

  float f;
  for (f = 0; f != 2.0; f += 0.4)
    cout << f << endl;
  cout << f << endl << endl;

  cout << "--------- boundary test -------------" << endl;
  f = 3.402823866e37;
  cout << f << endl;
  f = 3.402824036e37;
  cout << f << endl;
  f = 3.402824136e37;
  cout << f << endl << endl;

  f = 3.402823567e38;
  cout << f << endl;
  f = 3.402823568e38;
  cout << f << endl;
  f = 3.402823866e38;
  cout << f << endl << endl;

  return 0;
}