Simple c++ ATM (can't store balance variable input) - c++

Question

I'm making a simple c++ atm program, but I'm having trouble with getting the balance to change after I make a deposit or withdraw.
// C++ ATM
#include "std_lib_facilities.h"
int main()
{
bool card_is_inserted = false;
double balance = 0.0;
//double new_balance = balance;
// HOME
//Starts over if variable is false
while (card_is_inserted == false)
{
cout << "Wellcome to Well's Fargo ATM " << '\n'
<< "Insert card Yes or No"<< endl;
string request;
getline(cin,request);
// Function is needed for aceppting different no's and yes's
//-=-=-=--=-==--=-=-==-==-=--==--=-=-
// loads atm
if (request == "yes")
{
cout << "Alright, Your current balance is:" << endl
<< balance << endl;
card_is_inserted = true;
}
// home
string option = "cancel";
while (card_is_inserted == true)
{
cout << "Would you like to withdraw or deposit? (Cancel)"<< endl;
getline(cin,option);
double cash_ = 0;
if (option == "deposit")
{
cout << "How much money would you like to deposit?" << endl;
cin >> cash_;
double new_deposit_balance = balance + cash_;
cout << "You placed: $" << cash_ << endl
<< "Your New Balance is: $" << new_deposit_balance << endl;
}
if (option == "withdraw")
{
cout << "How much money would you like to withdraw?" << endl;
cin >> cash_;
double new_witdraw_balance = balance - cash_;
if(balance <= 0)
{
cout << "You don't have: $" << cash_ << endl;
}
else
{
cout << "You toke: $" << cash_ << endl
<< "Your New Balance is: $"<< new_witdraw_balance << endl;
}
}
if (option == "cancel")
{
cout << "Ok, bye" << endl;
card_is_inserted = false;
}
}
}
}
example: I type yes to make a deposit(or withdraw) and then place a simple double like 12.50 then it shows me my current balance which will be 12.50; afterward I want to make a withdraw of 12.00 with .50 left. But I cant because the balance variable didn't store my previous value which was 12.50. I tried making "double new_balance = balance" but doesn't work like in swift.

Answer 1

You are not setting balance to new_witdraw_balance or new_deposit_balance.
double new_deposit_balance = balance + cash_; doesn't set the balance value because you are bring in the value of balance, but you are not assigning the outcome of balance + cash_ to balance.
You need to put something like balance = new_witdraw_balance; and balance = new_deposit_balance; at the end of each if after cout statement.
if(option == "deposit")
{
cout << "How much money would you like to deposit?" << endl;
cin >> cash_;
double new_deposit_balance = balance + cash_;
cout << "You placed: $" << cash_ << endl << "Your New Balance is: $" << new_deposit_balance << endl;
balance = new_deposit_balance; // this
}
if(option == "withdraw")
{
cout << "How much money would you like to withdraw?" << endl;
cin >> cash_;
double new_witdraw_balance = balance - cash_;
if(balance <= 0)
{
cout << "You don't have: $" << cash_ << endl;
}
else
{
cout << "You toke: $" << cash_ << endl << "Your New Balance is: $"<< new_witdraw_balance << endl;
balance = new_witdraw_balance; // and this
}
}

Answer 2

The line double new_deposit_balance = balance + cash_; only assigns the new balance to new_deposit_balance, but then you don't do anything with that variable (except print the value). If you want the new balance to persist, you actually need to modify balance, not new_deposit_balance, so something like balance = balance + cash_; or balance += cash_;.
The variable double new_deposit_balance only exists in the if-block it's defined in, so once you leave the if-block, you lose the information in new_deposit_balance. On the other hand, since balance is defined outside your if-blocks and while-loops, its value will persist throughout your ATM operations.
Of course, you'd also need to apply the same fix to new_witdraw_balance.