Question

IN C++ PLEASE. Use ONLY: exception handling, read and write files, arrays, vectors, functions, headers and other files, loops, conditionals, data types, assignment.  

1. Calculating fuel economy. This program will use exceptions and stream errors to make a robust application that gets the number of miles and gallons each time the user fuels their car. It will put those values into vectors. Once the user wants to quit enter values, it will calculate the fuel economy.
   1. Create GetMiles() function that returns double.
      1. If there is a stream error, then throw a runtime_error with the message Invalid input received, you must enter a decimal number. Don’t forget to clear the error and ignore all characters until the end of the stream.
      2. If the value is less then or equal to zero, then throw a runtime_error with the message. Miles cannot be less than 0.
      3. Otherwise, return the miles the user entered
   2. Create GetGallons() function that returns double.
      1. If there is a stream error, then throw a runtime_error with the message Invalid input received, you must enter a decimal number. Don’t forget to clear the error and ignore all characters until the end of the stream.
      2. If the value is less than or equal to zero, then throw a runtime_error with the message. Gallons cannot be less than 0.
      3. Otherwise, return the miles the user entered
   3. Create GetMPG(vector<double miles, vector<double> gallons) function that returns a double.
      1. If the size of the vectors is 0, then throw a runtime_error with the message No values recorded MPG is nan
      2. Otherwise, total the miles and gallons and return the miles per gallon.
   4. The main program should loop and get the Gallons and Miles catching any exceptions that were thrown. Then ask if they want to enter another tank. If they enter gallons and miles put the values into the vectors given. When the user is done the program should calculate the MPG by calling GetMPG, catching the exception if the user did not enter any values. Then it should show the result.

Stream Errors

   cout << "Enter a number: " << endl;

   cin >> number;

  

   if (cin.fail()) {

      // Clear error state

      cin.clear();

      // Ignore characters in stream until newline

      cin.ignore(numeric_limits<streamsize>::max(), '\n');

      cout << "There was an error: " << endl;

     

   }

Throwing Errors

        throw runtime_error("Invalid value.");

Catching Errors

      try {

         // Code to try

      }

      catch (runtime_error &excpt) {

         // Prints the error message passed by throw statement

         cout << excpt.what() << endl;

      }

Make sure you include stdexcept and vector as well as the other standard modules.

Answer 1

// C++ program to calculate Fuel Economy

#include <iostream>
#include <stdexcept>
#include <limits>
using namespace std;

// function declaration
double GetMiles();
double GetGallons();
double GetMPG(vector<double> miles, vector<double> gallons);

int main()
{
vector<double> miles, gallons;
double in_miles, in_gallons;
char res;

// loop to input the miles and gallons and insert it into the vectors till the user wants
do
{
try
{
// input miles and gallons
in_miles = GetMiles();
in_gallons = GetGallons();
// insert the input into vectors
miles.push_back(in_miles);
gallons.push_back(in_gallons);
}catch(runtime_error &e)
{
// catch any exception raised
cout<<e.what()<<endl;
}
// ask if the user wants to enter another data
cout<<"Do you want to enter another tank (y/n)? ";
cin>>res;
}while(res == 'y' || res == 'Y');

// calculate and display the MPG
try{
cout<<endl<<"MPG: "<<GetMPG(miles, gallons);
}catch(runtime_error &e)
{
cout<<e.what()<<endl;
}
return 0;
}

// function that inputs miles from user and return it
double GetMiles()
{
double miles;
// input miles
cout<<"Enter the miles: ";
cin>>miles;
// check if there is any stream error
if(cin.fail())
{
cin.clear(); // clear the error
cin.ignore(numeric_limits<streamsize>::max(),'\n'); // ignore the characters until the end of line
throw runtime_error("Invalid input received, you must enter a decimal number.");
}else if(miles <= 0) // check if miles is less than or equal to 0
throw runtime_error("Miles cannot be less than 0");

return miles;
}

// function that inputs gallons from user and return it
double GetGallons()
{
double gallons;
// input gallons
cout<<"Enter the gallons: ";
cin>>gallons;
// check if there is any stream error
if(cin.fail())
{
cin.clear(); // clear the error
cin.ignore(numeric_limits<streamsize>::max(),'\n'); // ignore the characters until the end of line
throw runtime_error("Invalid input received, you must enter a decimal number.");
}else if(gallons <= 0) // check if gallons is less than or equal to 0
throw runtime_error("Gallons cannot be less than 0");

return gallons;
}

// function to calculate and return the miles per gallon (MPG)
double GetMPG(vector<double> miles, vector<double> gallons)
{
// check if the vectors contain any value
if(miles.size() == 0)
{
throw runtime_error("No values recorded MPG is nan");
}

// calculate the total miles and total gallons
double total_miles =0 , total_gallons = 0;
for(size_t i=0;i<miles.size();i++)
{
total_miles += miles[i];
total_gallons += gallons[i];
}
// calculate and return the MPG
return total_miles/total_gallons;
}

// end of program

Output: