Borland C++ Builder 2007, C++, MS Visual Studio 2010, Practice

С++. Developing a Random class for generating random numbers

Developing a Random class for generating random numbers

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Task

Develop a Random class that contains facilities for generating sequences of random numbers. Demonstrate the class. Develop the program as a Console Application.

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Solution

1. Declare internal variables min, max

In the first step, internal variables are introduced. In our case, in the private section, you need to enter variables with the following names:

  • min – the lower limit of the range of random numbers;
  • max – the upper limit of the range of random numbers.

Internal variables min, max are of type double. The class supports working with both integers and real numbers.

At this stage, the source code of the program is as follows:

#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;

// Class Random
class Random
{
private:
  double min, max; // range generating
}

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2. Class constructors

In the constructors, the code for setting the initial value (starting point) is placed for further generating sequences

srand(time(NULL));

This means that in the constructor for each created instance of the class, its own starting point is created. Each instance of the class will generate its own unique sequence of random numbers.

The text of the class constructors is as follows

...

// Class Random
class Random
{
private:
  double min, max; // range generating

public:
  // Class constructors
  // Constructor without parameters, initialize the number generator.
  // The default range is [0, 100].
  Random(double min, double max)
  {
    srand(time(NULL));

    // Correction if limits are incorrect
    if (max > min)
    {
      this->min = max;
      this->max = min;
    }
    else
    {
      this->min = min;
      this->max = max;
    }
  }

  // Constructor with two parameters that set the range
  // for generating random numbers
  Random(double min, double max)
  {
    srand(time(NULL));

    this->min = min;
    this->max = max;
  }
}

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3. Functions that generate single random numbers

When generating random numbers, the basic methods of the class are methods for generating single random numbers. The class implements the generation of both integers and floating point numbers.

3.1. Functions NextInt(). Generating integers

To generate integers, two functions are used, which differ in input parameters. One of the functions (with two parameters) receives the minimum and maximum values as input parameters, which form the range of the received number. Another function (without parameters) uses the value of the internal class variables min, max to form a range of generated numbers.

// A function to generate a random integer within the specified bounds.
// The range of numbers: [min, max]
int NextInt(int min, int max)
{
  // Get a random number - formula
  int num = min + rand() % (max - min + 1);
  return num;
}

// A function for generating a random integer
// based on the data of the current instance.
int NextInt()
{
  return NextInt((int)this->min, (int)this->max);
}

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3.2. Functions NextFloat(). Generating floating point numbers

To work with floating point numbers, the class implements two overloaded functions NextFloat(). One of the functions returns a floating point number for the range of values (min, max), which is specified as a function parameter. The second function returns a floating point number for the range of values (min, max), which is specified in the internal fields of the class instance.

Both functions are designed in such a way that they allow you to get a floating point number with a given precision. The precision is specified as an integer, which is equal to the number of decimal places.

The function text is as follows:

// A function that generates a random floating point number with a specified precision.
// Function gets 3 parameters:
// - min - lower limit;
// - max - upper limit;
// - precision - precision, number of decimal places.
double NextFloat(double min, double max, int precision = 2)
{
  double value;

  // get a random number as an integer with order precision
  value = rand() % (int)pow(10, precision);

  // get a real number
  value = min + (value / pow(10, precision )) * (max - min);

  return value;
}

// An overloaded version of NextFloat(), the function receives a parameter - precision.
// The range is determined based on the specified instance.
double NextFloat(int precision = 2)
{
  double value;

  // get a random number as an integer with order precision
  value = rand() % (int)pow(10, precision);

  // get a real number
  value = min + (value / pow(10, precision)) * (max - min);

  return value;
}

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4. Functions GetArrayInt() and GetArrayFloat(). Formation of sequences (arrays) of numbers

To extend the capabilities of the Random class, two additional functions have been introduced:

  • the GetArrayInt() function returns a pointer to an array of randomly generated integers;
  • the GetArrayFloat() function returns a pointer to an array of random floating point numbers.

The functions allocate memory for the resulting array. This memory needs to be freed after being used in the calling code.

// A method that returns an array of integers in the range
// set by the min, max values of the current instance.
// The input parameter count is the number of numbers in the array
int* GetArrayInt(int count)
{
  int* A = new int[count];
  for (int i = 0; i < count; i++)
    A[i] = NextInt();
  return A;
}

// A method that returns an array of real numbers in the range
// that is set in the current instance.
// Input parameters:
// - count - the number of numbers in the array;
// - precision - number of decimal places
double* GetArrayFloat(int count, int precision = 2)
{
  double* A = new double[count];
  for (int i = 0; i < count; i++)
    A[i] = NextFloat(precision);
  return A;
}

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5. Functions SetMinMax(), GetMin(), GetMax(). Access to the internal variables

Sometimes it becomes necessary to change or read the range of values that are generated by the methods of an instance of the Random class. For this, the class implements access methods for the min, max variables.

// ----------- Methods to access the internal variables----------------
void SetMinMax(double min, double max)
{
  this->min = min;
  this->max = min;
}

double GetMin()
{
  return min;
}

double GetMax()
{
  return max;
}

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6. Function main(). Demonstration of using the Random class

The main() function demonstrates the use of the Random class. The function text is as follows:

void main()
{
  // 1. Declare class instances
  Random R1(0, 5); // constructor with 2 parameters is called
  Random R2; // constructor without parameters is called

  // 2. Checking the NextInt() method
  int d1 = R1.NextInt();
  int d2 = R1.NextInt();

  cout << "d1 = " << d1 << endl;
  cout << "d2 = " << d2 << endl;

  // 3. Demonstration of the GetArrayInt() method
  int* D = R1.GetArrayInt(20); // memory is allocated for array D

  cout << "Array D: ";
  for (int i = 0; i < 20; i++)
    cout << D[i] << " ";
  cout << endl;

  delete[] D; // do not forget to free memory

  // 4. Initialization with another instance of the class
  Random R3 = R1;
  double* X = R3.GetArrayFloat(10, 4); // the memory is allocated

  cout << "Array X: ";
  for (int i = 0; i < 10; i++)
    cout << X[i] << " ";
  cout << endl;

  delete[] X; // free memory

  // 5. Set new limits on instance R1
  R1.SetMinMax(19, 13); // numbers in the range [13; 19]

  // Generate a new sequence in R1
  double* X2 = R1.GetArrayFloat(10, 3);

  cout << "Array X2:";
  for (int i = 0; i < 10; i++)
    cout << X2[i] << " ";
  cout << endl;

  delete[] X2;
}

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7. The text of the entire program (abridged version)

The abbreviated text of the Random class is as follows:

#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;

// Class Random
class Random
{
private:
  double min, max; // range generating

public:
  // ----------- Class constructors ----------------------
  // Constructor without parameters, initialize the number generator.
  // The default range is [0, 100].
  Random()
  {
    ...
  }

  // Constructor with two parameters that set the range
  // for generating random numbers
  Random(double min, double max)
  {
    ...
  }

  // ------ Methods for generating single random numbers --------
  // A function for generating a random integer
  // based on the data of the current instance.
  int NextInt()
  {
    ...
  }

  // A function to generate a random integer within the specified limits.
  // Range of numbers: [min, max]
  int NextInt(int min, int max)
  {
    ...
  }

  // A function that generates a random floating point number with the specified precision.
  double NextFloat(double min, double max, int precision = 2)
  {
    ...
  }

  // An overloaded version of NextFloat ()
  double NextFloat(int precision = 2)
  {
    ...
  }

  // ---------- Methods for generating sequences -------------------
  // A method that returns an array of integers in the range
  // set by the min, max values of the current instance.
  int* GetArrayInt(int count)
  {
    ...
  }

  // A method that returns an array of real numbers in the range that is set on the specified instance.
  double* GetArrayFloat(int count, int precision = 2)
  {
    ...
  }

  // ----------- Methods to access the internal variables ----------------
  void SetMinMax(double min, double max)
  {
    ...
  }

  double GetMin()
  {
    ...
  }

  double GetMax()
  {
    ...
  }
};

void main()
{
  ...
}

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Related topics

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