Population.cpp
PopulationDemo.cpp
Population.h
/* Population.h - Specification file of the Population class. */
#ifndef POPULATION_H
#define POPULATION_H
#include <string>
using std::string;
class Population
{
private:
string townName; // The name of a town
double birthRate; // The number of births p.A.
double deathRate; // The number of deaths p.A.
double startingPopulation; // The starting population
int numYears;
double populationIncrease; // Holds the population increase in percent
double populationDecrease; // Holds the population decrease in percent
double populationNetGrowth; // Holds the net population growth in percent
public:
Population() // Default constructor
{
townName = " ";
birthRate = 0.0;
deathRate = 0.0;
populationIncrease = 0.0;
populationDecrease = 0.0;
}
// Mutators
void setTownName(string tName);
void setNumYears(int nYears);
void setStartingPopulation(double sPop);
void setBirthRate(double bRate);
void setDeathRate(double dRate);
void calcPopulationIncrease(double sPop, double bRate, int numYrs);
void calcPopulationDecrease(double sPop, double dRate, int numYrs);
// Accessors
string getTownName() const
{ return townName; }
double getStartingPopulation() const
{ return startingPopulation; }
double getBirthRate() const
{ return birthRate; }
double getDeathRate() const
{ return deathRate; }
double getPopulationIncrease() const
{ return populationIncrease / 100.0; }
double getPopulationDecrease() const
{ return populationDecrease / 100.0; }
int getNumYears() const
{ return numYears; }
double getNetGrowth() const
{ return (populationIncrease / 100.0) - (populationDecrease / 100.0); }
double getNewPopulation() const
{ return (populationIncrease - populationDecrease) + startingPopulation; }
};
#endif
Population.cpp
/* Population.cpp - Implementation file for the Population class */
#include <cmath>
#include "Population.h"
/* **********************************************************
Population::setTownName
Assigns a value to the setTownName member variable. If the
field is not empty, the name passed to it is used, else a
default name is assigned to it.
********************************************************** */
void Population::setTownName(string tName)
{
if (!tName.empty())
{
townName = tName;
}
else
{
townName = "Terrania";
}
}
/* **********************************************************
Population::setStartingPopulation
Assigns a value to the startingPopulation member variable.
If the value is greater than 0, the value passed to it is
used, else the variable is set to 1,000.
********************************************************** */
void Population::setStartingPopulation(double sPop)
{
if (sPop > 0.0)
{
startingPopulation = sPop;
}
else
{
startingPopulation = 1000.0;
}
}
/* **********************************************************
Population::setBirthRate
Assigns a value to the birthRate member variable. If the
value is greater than 0, the value passed to it is used,
else the variable is set to 2.48.
********************************************************** */
void Population::setBirthRate(double bRate)
{
if (bRate > 0.0 && bRate <= 100.0)
{
birthRate = bRate;
}
else
{
birthRate = 2.48;
}
}
/* **********************************************************
Population::setDeathRate
Assigns a value to the deathRate member variable. If the
value is greater than 0 and lower than 100, the value
passed to it is used, else the variable is set to 1.15.
********************************************************** */
void Population::setDeathRate(double dRate)
{
if (dRate > 0.0 && dRate <= 100.0)
{
deathRate = dRate;
}
else
{
deathRate = 1.15;
}
}
/* **********************************************************
Population::setNumYears
Assigns a value to the numYears member variable. If the
value is greater 0, the value passed to it is used, else
the variable is assigned a default value of 5.
********************************************************** */
void Population::setNumYears(int nYears)
{
if (nYears > 0)
{
numYears = nYears;
}
else
{
numYears = 5;
}
}
/* **********************************************************
Population::calcPopulationIncrease
Calculates the population increase taking place over a
period of time.
********************************************************** */
void Population::calcPopulationIncrease(double sPop, double bRate, int numYrs)
{
populationIncrease += bRate * (pow((1 + bRate / 100.0), numYrs) * 10);
}
/* **********************************************************
Population::calcPopulationDecrease
Calculates the population decrease taking place over a
period of time.
********************************************************** */
void Population::calcPopulationDecrease(double sPop, double dRate, int numYrs)
{
populationDecrease += dRate * (pow((1 - dRate / 100.0), numYrs) * 10);
}
PopulationDemo.cpp
/* PopulationDemo.cpp - This program demonstrates the Population class. */
#include <string>
#include <iostream>
#include <iomanip>
#include "Population.h"
using std::cin;
using std::cout;
using std::fixed;
using std::showpoint;
using std::setprecision;
char tryAgain();
void getData(Population &);
void calcPopChange(const Population);
void displayStartData(const Population);
void displayPopChange(Population);
int main()
{
Population populous;
char again = ' ';
cout << "POPULOUS - Population Statistics Calculator\n";
do
{
getData(populous);
displayStartData(populous);
calcPopChange(populous);
again = tryAgain();
if (toupper(again) == 'N')
{
cout << "\nThank you for trying Populous! Have a nice day!";
}
} while (toupper(again) != 'N');
cin.ignore();
return 0;
}
/* **********************************************************
getData (accepts a reference to a Circle object)
The user is asked to input the following information:
* The town name (if the user leaves this field blank,
a default name is used)
* The starting population (if the user enters 0, a
default value of 1,000 is used)
* The number of births (if the user enters 0, a default
value of 2.48 is used)
* The number of deaths (if the user enters 0, a default
value of 1.15 is used)
* The number of years to calucalate population change
(If the user enters 0, a default value of 5 is used)
********************************************************** */
void getData(Population &populous)
{
string tName = " ";
double bRate = 0.0;
double dRate = 0.0;
double sPop = 0.0;
int numYrs = 0;
cout << "\nEnter the name of your town: ";
std::getline(cin, tName);
populous.setTownName(tName);
cout << "Enter the number of people currently living in your town: ";
cin >> sPop;
populous.setStartingPopulation(sPop);
cout << "Enter the annual birth rate of your town [Ex.: 2.48%]: ";
cin >> bRate;
populous.setBirthRate(bRate);
cout << "Enter the annual death rate of your town [Ex.: 1.15%]: ";
cin >> dRate;
populous.setDeathRate(dRate);
cout << "Enter the number of years you wish the simulation to run: ";
cin >> numYrs;
populous.setNumYears(numYrs);
}
/* **********************************************************
calcPopChange (accepts a Population object)
This function calculates the population increase and
decrease over a period of time.
********************************************************** */
void calcPopChange(Population populous)
{
for (int i = 0; i < populous.getNumYears(); ++i)
{
populous.calcPopulationIncrease(populous.getStartingPopulation(), populous.getBirthRate(), i);
populous.calcPopulationDecrease(populous.getStartingPopulation(), populous.getDeathRate(), i);
displayPopChange(populous);
}
}
/* **********************************************************
displayStartData (accepts a const Population object)
This function displays the initial values set by the user.
********************************************************** */
void displayStartData(const Population populous)
{
cout << "\nWelcome to " << populous.getTownName() << " Administrator!\n"
<< "This is the population you are starting with:\n"
<< "Number of people: " << populous.getStartingPopulation() << "\n"
<< "Number of births: " << populous.getBirthRate() << "% p.A.\n"
<< "Number of deaths: " << populous.getDeathRate() << "% p.A.\n";
}
/* **********************************************************
displayPopChange (accepts a const Population object)
This function displays the population change over a period
of time.
********************************************************** */
void displayPopChange(Population populous)
{
static int i = 0;
cout << "\nIn year " << (i += 1) << " the population of "
<< populous.getTownName() << " has grown to "
<< populous.getNewPopulation() << " people.\n\n";
cout << fixed << showpoint << setprecision(2);
cout << "Birth Rate: " << populous.getPopulationIncrease() << "%\n";
cout << "Death Rate: " << populous.getPopulationDecrease() << "%\n";
cout << "Net Growth: " << populous.getNetGrowth() << "%\n";
}
/* **********************************************************
Definition: tryAgain
This function asks the user if he or she wishes to try
again. This decision is returned.
********************************************************** */
char tryAgain()
{
char again = ' ';
cout << "\nDo you wish to try this again? ";
cin >> again;
cin.ignore();
/* Input validation */
while (toupper(again) != 'Y' && toupper(again) != 'N')
{
cout << "\nDo you wish to try this again? ";
cin >> again;
}
return toupper(again);
}
Example Output:
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