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;
}