Summing elements from a copied array in c++ - c++

Question

I've written a program that creates a restaurant menu through a text file, is opened up in another program and used to create a customer order.
I have a function which is needed to create the total amount at the end however the total sum is never produced, the program instead produces the total from itemPrice * itemQuantity and prints that instead of summing the final total.
I have the items saved in the menuItem array and am trying to copy them into a billingItems array to sum the prices in parallel. What step am I missing in order for total to sum up the prices, so total at the bottom would equal 44 (16+28) ?
Thank you
Creating the order in main():
int main(){
int i;
Item billingItem[MAX_ORDER];
Item menuItem[MAX_ORDER];
int itemNumber;
int itemQuantity;
int billOpt;
std::ofstream transactionFile;
transactionFile.open("transactionFile.txt");
int count = 0;
for(i = 0; i < MAX_ORDER; i++) {
std::cout << "Item number: ";
std::cin >> itemNumber;
i = itemNumber - 1;
std::cout << "Quantity: ";
std::cin >> itemQuantity;
menuItem[i].saveItemDetails(transactionFile);
std::cout << "\nWould you like to add another item?" << std::endl;
std::cout << "1. Yes\n2. No" << std::endl;
std::cin >> billOpt;
if (billOpt <= 0 | billOpt > 2) {
std::cout << "Error. Please enter a valid number: ";
std::cin >> billOpt;
}
if(billOpt == 2) { break; }
}
billingItem[i] = menuItem[i];
billingItem[i].calculateVAT(count, itemQuantity);
transactionFile.close();
the function within the implementation file:
void Item::calculateVAT(int count, int itemQuantity){
double total = 0.0;
double newItemPrice;
newItemPrice = itemPrice * itemQuantity;
total = newItemPrice + total;
//extra couts to see what is happening
std::cout << "ITEM QUANTITY" << itemQuantity <<"\n";
std::cout << "TOTAL" << total <<"\n";
}
what is produced when running the program:
Item: 2| Category: Meat| Description: Pork Chops| Price: £8
COUNT3
ITEM QUANTITY2
TOTAL16
Item: 3| Category: Meat| Description: Ribs| Price: £14
COUNT4
ITEM QUANTITY2
TOTAL28

Answer 1

You could declare total as static in the function so it is only initialized once.
void Item::calculateVAT(int count, int itemQuantity){
static double total = 0.0;
double newItemPrice;
newItemPrice = itemPrice * itemQuantity;
total += newItemPrice ; //
//extra couts to see what is happening
std::cout << "ITEM QUANTITY" << itemQuantity <<"\n";
std::cout << "TOTAL" << total <<"\n";
}
Another solution would be to declare a total variable in the main and modify your function signature.
That would imply printing total from your main.
calculateVAT function :
double Item::calculateVAT(int count, int itemQuantity)// No more void
{
double total = 0.0; // this one only serves in the function scope
double newItemPrice;
newItemPrice = itemPrice * itemQuantity;
total = newItemPrice + total;
//extra couts to see what is happening
std::cout << "ITEM QUANTITY" << itemQuantity <<"\n";
std::cout << "TOTAL" << total <<"\n";
return total; // this number will add up in the main
}
Your main :
int main(){
int i;
Item billingItem[MAX_ORDER];
Item menuItem[MAX_ORDER];
int itemNumber;
int itemQuantity;
int billOpt;
double total = 0.0; // this here will serve as the sum of all your items prices
std::ofstream transactionFile;
transactionFile.open("transactionFile.txt");
int count = 0;
for(i = 0; i < MAX_ORDER; i++) {
std::cout << "Item number: ";
std::cin >> itemNumber;
i = itemNumber - 1;
std::cout << "Quantity: ";
std::cin >> itemQuantity;
menuItem[i].saveItemDetails(transactionFile);
std::cout << "\nWould you like to add another item?" << std::endl;
std::cout << "1. Yes\n2. No" << std::endl;
std::cin >> billOpt;
if (billOpt <= 0 | billOpt > 2) {
std::cout << "Error. Please enter a valid number: ";
std::cin >> billOpt;
}
if(billOpt == 2) { break; }
}
billingItem[i] = menuItem[i];
total += billingItem[i].calculateVAT(count, itemQuantity); // modified here``
std::cout << "TOTAL" << total << std::endl;
transactionFile.close();
For reference, I have made a simple code with a basic situation :
void calculateVAT(int count, int itemQuantity) { // Static version, is initialized only once and then only gets updated
static double total = 0;
double newItemPrice;
newItemPrice = 10 * itemQuantity;
total += newItemPrice ;
//extra couts to see what is happening
std::cout << "ITEM QUANTITY " << itemQuantity << "\n";
std::cout << "TOTAL from function " << total << "\n";
}
double d_calculateVAT(int count, int itemQuantity) { // Non void version, returns a sum to a variable in the main
double sum = 0;
double newItemPrice;
newItemPrice = 10 * itemQuantity;
sum += newItemPrice;
return sum;
}
int main()
{
int itemQty = 5;
double sum = 0; // if you want to call it from the main
calculateVAT(0, 4); // void version with static - will update its total variable as 40
calculateVAT(0, 7); // void version with static - will update its total variable as 40 + 70 = 110
sum+=d_calculateVAT(0, 4); // double version - will return sum = 40
sum+=d_calculateVAT(2, 7); // double version - will return sum + 70 = 110
std::cout << "TOTAL from main " << sum << std::endl;
while (1)
{ }
return 0;
}
Also, maybe it's for another purpose, but I don't see the point of the variable "count" sent to calculateVAT, it's not used in the function.