C++ Project: converting a interger into a double

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;
   }
   

</details>
# 答案1
**得分**: 0
替代这个：
```cpp
int Population::getBirthrate()
{
return births / population;
}

使用这个：

int Population::getBirthrate()
{
   return (births * 1.0) / population;
}

将一个整数与1.0相乘将其转换为双精度浮点数。

int Population::getBirthrate()
{
return births / population;
}

int Population::getBirthrate()
{
return (births * 1.0) / population;
}

答案2

得分: 0

我猜你有两个问题

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

第一个问题就是，正如你已经指出的，你在进行整数除法。你可以通过使用类型转换解决这个问题。第二个问题是，你的函数返回一个整数，而从上面的问题看来，你想要一个浮点数的结果，例如 10/100 = 0.1。解决这个问题的方法是将返回类型更改为 double。

因此，将这两个问题合并在一起：

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

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

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