C++ Project: converting a interger into a double

Question

Hi to all I am new to programming with C++, and I have been assigned a project where I have to build a program that calculates the average birthrate & death rate percentage of a population. I am currently stuck on this step where I need to convert an integer value into a double value to get the correct output. For example, a function for finding the birthrate would be (births/population) and since dividing integers it causes the floating point number to be truncated giving me a result of 0 instead of getting (10/100 which would equal 0.1). I understand that I have declared integers, but that is the requirement. I have thought about typecasting but had no luck converting the value. I apologize for the long explanation I hope it makes sense. Thank you in advance!

This is the following criteria:

1. private variables: have to be integers (population, births, deaths)

2. public functions:

• default constructor with no parameters, initialize (population = 2), (births & deaths = 0)
• constructor with three parameters. The constructor should pass the population, the number of births, and deaths for the Population object.

3. "Set" member function for each of the three-member variables. If a population figure is less than 2 and is passed to the class, use a default value of 2. If a birth or a death figure less than 0 is passed, use a default value of 0.

4. getBirthrate member function. calculates the birth rate based on the following formula: (Birthrate = Number of births/population)

5. getDeathrate member function. calculates the death rate based on the following formula: (Deathrate = Number of deaths/ population)

   #include <iostream>
   #include <string>
   #include <iomanip>
   using namespace std;
   
   
   //  Population class declaration
   class Population
   {
   private:
       int population, births, deaths;
   
   public:
       // default constructor: with no parameters
       Population()
       {
           population = 2;
           births = 0;
           deaths = 0;
       }
   
       // constructor
       Population(int p, int b, int d)
       {
           population = p;
           births = b;
           deaths = d;
       }
   
       // birthrate member function
       int getBirthrate();
       // deathrate member function
       int getDeathrate();
   
       void setPopulation(int);
       void setBirth(int);
       void setDeath(int);
       int getPopulation();
       int getBirth(int);
       int getDeaths(int);
   };
   
   // member functions
   void Population::setPopulation(int p)
   {
       if (population < 2)
       {
           population = 2;
           cout << "Error: Invalid population input!" << endl;
       }
       else
       {
           population = p;
       }
   }
   
   void Population::setBirth(int b)
   {
       if (births < 0)
       {
           births = 0;
           cout << "Error: Invalid births input!" << endl;
       }
       else
       {
           births = b;
       }
   }
   
   void Population::setDeath(int d)
   {
       if (deaths < 0)
       {
           deaths = 0;
           cout << "Error: Invalid deaths input!" << endl;
       }
       else
       {
           deaths = d;
       }
   }
   
   int Population::getPopulation()
   {
       return population;
   }
   
   int Population::getBirth(int)
   {
       return births;
   }
   
   int Population::getDeaths(int)
   {
       return deaths;
   }
   
   // calculating functions
   int Population::getBirthrate()
   {
       return births / population;
   }
   
   int Population::getDeathrate()
   {
       return deaths / population;
   }
   
   // main function
   int main()
   {
       // instantiation of a population object
       Population x;
   
       int xBirths, xDeaths, xPopulation;
   
       // getting the values
       cout << "What is the population: " << endl;
       cin >> xPopulation;
   
       cout << "What is the number of births: " << endl;
       cin >> xBirths;
   
       cout << "What are the number of deaths: " << endl;
       cin >> xDeaths;
   
       // set functions
       x.setPopulation(xPopulation);
       x.setBirth(xBirths);
       x.setDeath(xDeaths);
   
       // calculating the values
       cout << "The population is: " << x.getPopulation() << endl;
       cout << "The birthrate is: " << x.getBirthrate() << endl;
       cout << "The deathrate is: " << x.getDeathrate() << endl;
   
       return 0;
   }
   

Answer 1

I would guess that you have two problems

int Population::getDeathrate()
{
    return deaths / population;
}

The first is, as you've identified, you are doing integer division. You can solve that with a type cast. The second problem is that your function returns an integer, when it seems from the question above that you want a floating point result, e.g. 10/100 = 0.1. The solution to that problem is to change the return type to double.

So, putting both of those together

double Population::getDeathrate()
{
    return (double)deaths / (double)population;
}