Question

I’m trying to write a program that

• Defines an array of five circles objects where radius is set using the random number provided by the random class utilising the parameterised constructor

• Defines a second array of five circles objects where radius is set using the random number provided by the random class utilising the setRadius method

• Displays the areas of each circle within each array using getArea()

The problem I need help with to display the areas of each circle within each array using getArea() method, I need to access the array which has the radius values of five circle in each array and then work out the area 3.14 * Radius * Radius. Then display the area to the screen.

Also after doing some research, do I need to Instantiate Circle object
which I entered in Circle myCircle;. However it came with an error saying

1>main.obj : error LNK2019: unresolved external symbol “public:
__thiscall Circle::Circle(void)” (??0Circle@@QAE@XZ) referenced in function _main

Circle.h file

#pragma once
#include <string>

class Circle 
{
private:
    float Radius;

public:
    Circle(); // initialised radius to 0
    Circle(float r); // accepts an argument and assign its value to the radius attribute
    void setRadius(float r); // sets radius to a value provided by its radius parameter (r)
    float getRadius(); // returns the radius of a circle
    float getArea(); // calculates and returns the areas of its circle
};

Random.h file

#pragma once
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

class Random
{
public:
    static void initialiseSeed();
    // random number initialised
    // random number has been initialised to the current time.

    static int random(int lower, int upper);
    // this function will return a positive random number within a specific lower and 
    // upper boundary.
};

Main.cpp file

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <iomanip>
using namespace std;

// Include header files
#include "Circle.h"
#include "Random.h"

int main()
{
    // Instantiate myCircle object
    //Circle myCircle;

    // Array 1
    // an array of five circles objects where radius is set using the random number
    // provided by the random class utilising the parameterised constructor

    int CircleArrayOne [5]; // store the numbers
    const int NUM = 5; // Display 5 random numbers

    srand(time(NULL)); // seed the generator

    // populate the array by calling the random function from the random class
    // within the lower and upper bounds

    for(int x = 0; x < NUM; ++x)
    {
        CircleArrayOne[x] = Random::random(1, 40); // assumed 0 and 40 as the bounds
    }

    // Below is the code I use to output the array to the screen to make sure
    // that is output the correct number of values and it generate number between 1 and 40
    // I am doing this to test the code above that populate the array within lower and upper
    // bounds

    cout << "Checking the radius in the Array 1." << endl;
    for(int i = 0; i < NUM; ++i) 
    {
        cout << CircleArrayOne[i] << endl;
    }

    // Array 2
    // a second array of five circles objects where radius is set using the random number 
    // provided by the random class utilising the setRadius method

    float CircleArrayTwo [5]; // store the numbers
    const int Number = 5; // Display 5 random numbers

    srand(time(NULL)); // seed the generator

    // populate the array with random numbers

    for(int i = 0; i < Number; ++i)
    {
        CircleArrayTwo[i] = rand()%100;
    }

    // Below is the code I use to output the array to the screen to make sure
    // that is output the correct number of values and it generate random values

    cout << "Checking the radius in the Array 2." << endl;
    for(int i = 0; i < Number; ++i)
    {
        cout << CircleArrayTwo[i] << endl;
    }

    // Display the area of each Circle within each array using getArea()

    cout << "\nThe area of each circle within array 1: " << endl;

    cout << "\nThe area of each circle within array 2: " << endl;

    // Display a message that indicates which set of circle has the largest 
    // combined area

    cout << "\nArray: " << "had the largest combined area." << endl;

    // Display a message that indicates which set contains the circle 
    // with the largest area

    cout << "\nArray: " << "contain the circle with the largest area.\n" << endl;

    system("PAUSE");
    return 0;
}

// Calling Circle(float r) from Circle Class
Circle::Circle(float r)
{
    if (r<=0)
    {
        cout << "An invalid radius has been detected." << endl;
        cout << "The radius has been set to 1.0" << endl;
        Radius = 1.0;
    }
    else
        Radius = r;
}

// Calling getArea() from Circle Class
float Circle::getArea()
{
    // Area = pi * radius * radius
    return 3.14 * Radius * Radius;
}

// Calling setRadius(float r) from Circle Class
void Circle::setRadius(float r)
{
    rand()%100;
    Radius = r;
}

// Calling getRadius() from Circle Class
float Circle::getRadius()
{
    return Radius;
}

// Calling random(int lower, int upper) from Random Class
int Random::random(int lower, int upper)
{
    int range = upper - lower + 1;
    return (rand() % range + lower);
}

// Calling initialiseSeed() from Random Class
void Random::initialiseSeed()
{
    srand((unsigned int)time(0));
    rand()%100;
}

How do I get the area of each circle within each array using getArea() function

Answer 1

You haven’t provided a definition for Circle‘s default constructor, add

Circle::Circle() : Radius(0) {}

to main.cpp.