Question
Write the definition for a class named GasPump to be used to model a pump at an automobile service station. Before you go further with this programming exercise, write down the behavior you expect from a gas pump from the point of view of the purchaser.
The following are listed things a gas pump might be expected to do. If your list differs, and you think your list is as good or better than these, then consult your instructor. You and your instructor should jointly decide what behavior you are to implement. Then implement and test the agreed upon design for a gas pump class.
a. A display of the amount dispensed
b. A display of the amount charged for the amount dispensed
c. A display of the cost per gallon, liter, or other unit of volume that is used
where you reside
d. Before use, the gas pump must reset the amount dispensed and amount
charged to zero.
e. Once started, a gas pump continues to dispense fuel, keep track of the
amount dispensed, and compute the charge for the amount dispensed until
stopped.
f. A stop dispensing control of some kind is needed.
Implement the behavior of the gas pump as declarations of member functions of the gas pump class, then write implementations of these member functions. You will have to decide if there is data the gas pump has to keep track of that the user of the pump should not have access to. If so, make these private member variables.
Answer
C++ program code:
#include <iostream>
using namespace std;
//Create GasPump class is defined, which encapsulates
//the behavior and data of a gas pump.
class GasPump
{
private:
//Declare variables
double amountDispensed;
double amountCharged;
double costPerUnit;
public:
//Constructor with parameter
GasPump(double cost)
{
amountDispensed = 0.0;
amountCharged = 0.0;
costPerUnit = cost;
}
//The reset member function resets the
//amountDispensed and amountCharged to zero.
void reset() {
amountDispensed = 0.0;
amountCharged = 0.0;
}
//The startDispensing member function takes a volume parameter
//and updates the amountDispensed and amountCharged based on the provided volume and the cost per unit.
void startDispensing(double volume) {
amountDispensed += volume;
amountCharged += volume * costPerUnit;
}
//The stopDispensing member function simply outputs
//a message indicating that dispensing has stopped
void stopDispensing() {
cout << "Dispensing stopped." << endl;
}
//The displayAmountDispensed, displayAmountCharged, and
//displayCostPerUnit member functions output the corresponding information to the console.
void displayAmountDispensed() {
cout << "Amount dispensed: " << amountDispensed << endl;
}
void displayAmountCharged() {
cout << "Amount charged: " << amountCharged << endl;
}
void displayCostPerUnit() {
cout << "Cost per unit: " << costPerUnit << endl;
}
};
//Program begins with a main method
int main() {
GasPump pump(2.5); // Create a gas pump with a cost of 2.5 per unit
pump.reset(); // Reset the pump before use
pump.startDispensing(10.0); // Start dispensing 10 units
pump.startDispensing(5.0); // Continue dispensing 5 units
pump.displayAmountDispensed(); // Display the amount dispensed
pump.displayAmountCharged(); // Display the amount charged
pump.displayCostPerUnit(); // Display the cost per unit
pump.stopDispensing(); // Stop the dispensing
return 0;
}
Output of the program code:
Amount dispensed: 15
Amount charged: 37.5
Cost per unit: 2.5
Dispensing stopped.