I want to build a cafe in C++. I want the user to answer each question with a yes or no. If they answer yes or no, I want to display their total price.

#include <iostream>
using namespace std;
int main()

 //Develop a billing statement for a store/restaurant 
 // Define variables 
 double donut, bagel, burrito, sandwhich, omelet, coffee, cappachino, smootie, water, spirit, total, tax;
 char answerType;
 bagel = 2.50;
 burrito = 3.50;
 donut = 1.00;
 sandwhich = 3.50;
 omelet = 1.25;
 coffee = 1.50;
 cappachino = 2.00;
 smootie = 3.25;
 water = 0.99;
 spirit = 1.00;
 total = 0.00;
 tax = 6.25;
 cout << "Welcome to Junelle's Cafe" << endl;
 // Introduction to my cafe

 //Customer knows the options before hand 
 //Customer enters yes (y) or no (n) 
 cout << "Enter a y (yes) or no (n) for every question asked." << endl;

//Ask user if they want a bagel 
 cout << "Would you like to buy a bagel for $2.50?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A bagel has been added to your order. Your total is " << total + bagel << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item2
 cout << "Would you like to buy a donut for $1.00?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A donut has been added to your order. Your total is " << total + donut+bagel << endl;

 


 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item3 
 cout << "Would you like to buy a omelet for $1.25?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A omelet has been added to your order. Your total is " << total + donut + bagel+ omelet << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item 4
 cout << "Would you like to buy a burrito for $2.50?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A burrito has been added to your order. Your total is " << total + donut + bagel
 + omelet + burrito << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 

//item 5 
 cout << "Would you like to buy a sandwhich for $2.50?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A sandwhich has been added to your order. Your total is " << total + donut + bagel
 + omelet+ burrito+sandwhich << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item 6
 cout << "Would you like to buy a coffee for $1.50?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A coffee has been added to your order. Your total is " << total + donut + bagel 
 + omelet+ burrito + sandwhich + coffee<< endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 

//item 7 
 cout << "Would you like to buy a cappachino for $2.00?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A cappachino has been added to your order. Your total is " << total + donut + bagel 
 + omelet + burrito + sandwhich + coffee+ cappachino << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item 8
 cout << "Would you like to buy a water for $0.99?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A water has been added to your order. Your total is " << total + donut + bagel
 + omelet + burrito + sandwhich + coffee + cappachino + water << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item 9 
 cout << "Would you like to buy a spirit for $1.00?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A spirit has been added to your order. Your total is " << total + donut + bagel
 + omelet + burrito + sandwhich + coffee + cappachino + water + spirit<< endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 
//item 10 
 cout << "Would you like to buy a smootie for $1.25?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A smootie has been added to your order. Your total is " << total + donut + bagel 
 + omelet + burrito + sandwhich + coffee + cappachino + water + spirit + smootie << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 

 cout << "Thank you for visiting Junelle's Cafe" << endl;
 while (1);
 return 0;

Don't. Repeat. Yourself.

That's an essential principle. You repeat the "do you want XY" cycle over and over manually. That's not only error prone, but also hard to maintain. For example, let's say you want to ask the customer how many items they want. Then you would have to add or change your input handling for every single item.

Maybe you want to use

 15 bagels
200 coffee
 1 water
 1 donut

It would get rather tedious to do that in your current program. We would need int bagelCount, coffeeCount, waterCount, coconoutCount…, you get the pattern.

So instead, we should try to handle all the items the same way in a single block of code, if possible. Which brings us to the next topic.

Reuse information

At the begin of your program, you have bagel = 2.50. However, you don't use that information to your advantage when you ask the customer whether they want to buy a bagel:

cout << "Would you like to buy a bagel for $2.50?:";
 ^^^^^^

That's again a DRY violation. If you change the bagel price, you have to change it at two places. That's error prone. Instead, reuse the information you already have at hand:

std::cout << "Would you like to buy a bagel for $" << bagel << ": ";

By the way, if a variable should never change its value, declare it const. Also, try to initialize your variables, with a value, whenever possible:

typedef double Price;

const Price bagelPrice = 2.50;
const Price coffeePrice = 1.50;

But we will change that later, so don't use that yet.

Don't trust the customer

What happens if the customer inputs 'a' instead of 'y' or 'n'? Well, you accept it and don't add anything.

However, if you asked a customer "Do you want a bagel?" and they answer "Cthulhu!", you'd probably ask them to either accept your offer or decline. A small

bool ask_yes_no() 
 /* exercise */

function can help you.

Namespaces

Unless you know what you're doing don't use using namespace std.

Abstractions

Now let's have a look at one item exchange

//Ask user if they want a bagel 
 cout << "Would you like to buy a bagel for $2.50?:";
 cin >> answerType;

 if (answerType == 'y')

 

 cout << "A bagel has been added to your order. Your total is " << total + bagel << endl;

 

 else if (answerType == 'n')

 
 cout << "Your total is " << total << endl;

 

All other items follow the same structure, so lets focus on this one. We see a pattern here:

1. We say the name of the product and the price


2. We ask whether they want to buy the product


3. We add the item to the order and increase the total (this step is missing)


4. We tell the customer their new total


5. If we still have products, we select the next product and continue with 1.


6. Otherwise we tell the customer the total.

Therefore, let us rewrite that dialog:

std::cout << "Would you like to buy a " << item_name
 << " for $" << item_price << ": ";

if(asks_yes_no()) // see exercise above
 total += item_price;

 std::cout << "A " << item_name<< " has been added to your order. ";


std::cout << "Your total is $" << total << ".";

Now all we need is a way to get item_name and item_price and traverse all items. There are several ways:

• we can use an associative collection, e.g. std::map<Name, Price>
  


• we can couple the name and the price in a single Item and use a normal collection std::vector<Item>
  

The other review uses the latter, therefore let us have a look at the former, a std::map:

typedef std::string ItemName
typedef double Price;

const std::map<ItemName, Price> menu 
 "bagel", 2.50 ,
 "coffee", 1.50 ,
 "sugar", 0.02 ,
 "full breakfast", 5.00
;

We can now traverse all items in the menu easily:

// You might not know this kind of loop yet.
// It's basically going through the menu.
// The current pair of item and price is item_and_price,
// the .first-Member is the item, and the .second-Member
// is the price.
//
// The following holds throughout the loop:
//
// menu[item_and_price.first] == item_and_price.second
for(const auto & item_and_price : menu) 
 const auto & item_name = item_and_price.first;
 const auto & item_price = item_and_price.second;

 std::cout << "Would you like to buy a " << item_name 
 << " for $" << item_price << ": ";

 if(asks_yes_no()) // see exercise above
 total += item_price;

 std::cout << "A " << item_name << " has been added to your order. ";
 

 std::cout << "Your total is $" << total << ".";

We can also keep tracks of the order:

typedef unsigned int Amount;

std::map<ItemName, Amount> order;

/* ... */

total += item_price;

order[item_name] = 1;

Small remark on the floating point values

Floating point arithmetic isn't exact. Instead of double, we should use an exact type and cents instead of a floating point type and dollars, e.g.

const Cents bagelPrice = 250;

For a small toy program, double is fine. But if you ever handle real money in your code, make sure that neither the customer, you, or the government pay too much or don't get enough money.

Usability

Last, but not least, you can show the menu to the user and have them pick the item they want to buy, e.g.:

Welcome to our shop. We have the following products at hand:

 1) Bagel ($2.50)
 2) Coffee ($1.50)
 3) Espresso ($1.50)
 4) Breakfast ($5.20)
 5) Checkout

Your choice? [1-5]: 1

Amount of bagels: 20

Your order of 20 bagels has been registered. Your new total is $50.00.

---- ---- ----

 1) Bagel ($2.50)
 2) Coffee ($1.50)
 3) Espresso ($1.50)
 4) Breakfast ($5.20)
 5) Checkout

You ordered 20 bagels. Your next choice [1-5]: 5

Your total is $50.00. Thanks for visiting and come again!

That way they don't have to go through all the products if they just want to buy 20 bagels.

This is a very straightforward way to implement this, and it's very easy to read. That's great! But it might have occurred to you that there's an easier way. Here are some thoughts on simplifying it.

Use Classes

Notice how you have several items that all have the same properties. They all have a name and a price. So it would make sense to combine those into a class. A simple class might be something like this:

class InventoryItem 
 public:
 InventoryItem (const std::string& itemName, const double itemPrice);
 ~InventoryItem();

 std::string getName() const;
 double getPrice() const;

 private:
 std::string name;
 double price;
;

The constructor of the class would simply set the name field to the passed in item name, and the price field to the passed in item price:

InventoryItem (const std::string& itemName, const double itemPrice) : 
 name (itemName), 
 price(itemPrice) 

The get functions would just return the values:

std::string getName() const

 return name;

Once you have a class for this, you can create objects by doing something like this:

InventoryItem newItem("burrito", 3.50);

Use Arrays

Since you have several items and you want to do similar operations on them, you can put them into an array. An array holds multiple items of the same type. So in this case, we'd want an array of InventoryItems. We can create one like this:

#include <array>

int main()

 std::array<InventoryItem, 10> inventory 
 InventoryItem("bagel", 2.50),
 InventoryItem("burrito",3.50),
 InventoryItem("donut", 1.00),
 InventoryItem("sandwhich", 3.50),
 InventoryItem("omelet", 1.25),
 InventoryItem("coffee", 1.50),
 InventoryItem("cappachino", 2.00),
 InventoryItem("smootie", 3.25),
 InventoryItem("water", 0.99),
 InventoryItem("spirit", 1.00)
 ;

When you have items in an array and you want to do the same thing to each item, you can iterate over them in a loop. An array is a type of "container" because it holds other objects. All containers supplied by the standard template library (that's the std:: prefix stuff) supply objects called iterators that allow you to step through each item in the container. You simply call container.begin() to get the iterator that points to the first item in the container, then increment it to get the next one. You can keep incrementing it until it is equal to container.end(), and then you know you don't have any more to process. So let's try that with the above array of inventory items:

for (std::array<InventoryItem, 10>::iterator nextItem = inventory.begin();
 nextItem != inventory.end();
 nextItem++)

 std::cout << "Would you like to buy a " << nextItem->getName();
 std::cout << " for " << nextItem->getPrice() << "?n";

 std::cin >> answerType;

 if (answerType == 'y')
 
 std::cout << "A " << nextItem->getName();
 std::cout << " has been added to your order. Your total is ";
 std::cout << total << "n";
 
 else
 
 std::cout << "Your total is " << total << "n";
 

Now notice something odd about the total? It's not getting updated properly. I didn't add the cost of the item into the total. The reason I didn't is because I want you to look at how you did it in your version. In your first if statement, if the user chooses "y", you print out total + bagel. But notice that you didn't actually update total, you only printed it. You need to actually assign the new price to total. So you need to do something like this:

total = total + bagel;

Or in my version with the array and loop, it would just be:

total = total + nextItem->getPrice();

Notice also that in your version, for the second if statement, when the user chooses "y" you print the price of a bagel and a donut. But what if the user chose "n" for bagel and "y" for donut? You'll print the wrong price!

So if you keep track of the total as you go, and update it after every "y" choice, then it should always have the right value, and you won't need to manually add in all the other choices.

And you can end it just as you end your version:

cout << "Thank you for visiting Junelle's Cafe" << endl;
while (1);
return 0;

Thanks for letting us drop in!