Needing help with my loop

[akeilo]

I was wondering how I could fix this loop to keep asking the user to input a number after the wrong number. I also am trying to figure out what I broke.
Thank you for all the help and I hope you have a happy Easter!

  #include <iostream>
#include <string>
#include <iomanip>
using namespace std;
int main()
{
    string product = ""; // this variable is used to store the product bought
    int input; // to store user input
    cout << "What would you like to buy?" << endl;
    cout << "1. Bread:" << endl;
    cout << "2. Milk:" << endl;
    cout << "3. Soap:" << endl;
    cout << "4. Eggs:" << endl;
    cout << "5. Deodorant:" << endl;
    cout << "6. Juice:" << endl;
    cout << "7. Chips:" << endl;
    cout << "8. Forks:" << endl;
    cout << "9. Spoons:" << endl;
    cout << "10. Cups:" << endl;
    cout << "Please enter your choice: ";
    cin >> input; // getting user input
    
if (input < 1 || input > 10)
    {
        cout << "Sorry, "<<input<<" wasn’t a valid choice" << endl;
        cout << "Please enter choice: ";
        cin >> input;
    }
    
    {
        if (input == 1)
        {
        product = "Bread";
        }
        else if (input == 2)
        {
        product = "Milk";
        }
        else if(input == 3)
        {
        product = "Soap";
        }
        else if(input == 4)
        {
        product = "Eggs";
        }
        else if(input == 5)
        {
        product = "Deodorant";
        }
        else if(input == 6)
        {
        product = "Juice";
        }
        else if(input == 7)
        {
        product = "Chips";
        }
        else if(input == 8)
        {
        product = "Forks";
        }
        else if(input == 9 )
        {
        product = "Spoons";
        }
        else if(input == 10)
        {
        product = "Cups";
        }

    if (product != "")
    {
        float price; // To store price of product
        int age; // to store age of customer
        cout << "Please enter price for "<<product<<": $"; // Asking the user for price
        cin >> price;
        cout << "Please enter your age: "; // Asking the user for age
        cin >> age;
        float tax = 0;
        if (product == "Soap","Deodorant") // If product is not grocery
        {
            tax = 0.08 * price; // Calculating tax
        }
        
        float discount = 0;
        if (age >= 60) // If age is greater than 60
        {
            discount = 0.05 * price; // Calculating discount
        }
        cout << "Invoice " << endl;
        cout << "-----------" << endl;
        cout << product << " price: $" << fixed << setprecision(2) << price << endl;
        cout << "Tax: $" <<fixed<<setprecision(2)<<tax <<endl;
        if (discount > 0)  // If discount greater than 0 
        {
            cout << "Discount: $-"<<fixed << setprecision(2) << discount << endl;
        }
        float total = price + tax - discount; // Calculating total price
        cout << "Total: $" << fixed << setprecision(2)<<total << endl; // Displaying total price
    }
}

[keskiverto]

Your program does not contain any loops.

What does condition in line 81 do?


A lookup table would shorten your code.

vector<string> types[] { "", "Bread", "Milk" };
for ( int i=1; i<types.size(); ++i ) cout << i << ". " << types[i] << '\n';
if ( 0<input and input<types.size() ) product = types[input];

[seeplus]

keep asking the user to input a number after the wrong number

Consider which only allows valid input:

#include <iostream>
#include <string>
#include <iomanip>
#include <limits>
using namespace std;

int getInt(const std::string& prm)
{
	int i {};

	while ((std::cout << prm) && (!(std::cin >> i) || std::cin.peek() != '\n')) {
		std::cout << "Not an integer\n";
		std::cin.clear();
		std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
	}

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

double getNum(const std::string& prm)
{
	double i {};

	while ((std::cout << prm) && (!(std::cin >> i) || std::cin.peek() != '\n')) {
		std::cout << "Not a number\n";
		std::cin.clear();
		std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
	}

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

int main()
{
	constexpr const char* const products[] {"Bread", "Milk", "Soap", "Eggs", "Deodorant", "Juice", "Chips", "Forks", "Spoons", "Cups"};

	cout << "What would you like to buy?\n";

	for (size_t no = 0; const auto & p : products)
		std::cout << std::setw(2) << ++no << "  " << p << '\n';

	int input {};

	while ((input = getInt("Please enter your choice: ")) < 1 || input > 10)
		cout << "Sorry, " << input << " isn't a valid choice\n";

	const string product {products[input - 1]};
	const auto price {getNum("Please enter price for " + product + ": $")};
	const auto age {getInt("Please enter your age: ")};
	const auto tax {product == "Soap" || product == "Deodorant" ? 0.08 * price : 0.0};
	const auto discount {age >= 60 ? 0.05 * price : 0.0};

	cout << "Invoice\n";
	cout << "-----------\n";
	cout << product << " price: $" << fixed << setprecision(2) << price << '\n';
	cout << "Tax: $" << fixed << setprecision(2) << tax << '\n';

	if (discount > 0)
		cout << "Discount: $-" << fixed << setprecision(2) << discount << '\n';

	const auto total {price + tax - discount};

	cout << "Total: $" << fixed << setprecision(2) << total << '\n';
}

[Handy Andy]

Hello akeilo,

Here is something to think about:

#include <iostream>
#include <iomanip>
#include <limits>  // <--- Added.
#include <string>

using namespace std;

int main()
{
    constexpr int MINCHOICE{ 1 }, MAXCHOICE{ 10 };  // <--- Change "MAXCHOICE" if menu choices change.
    //constexpr double prices[]{ 0.0, 1.50, 2.50 };  // <--- Why are you letting the user enter a price?

    string product; // this variable is used to store the product bought. Empty when defined. Does not need initialized.
    int input; // to store user input

    std::cout << std::fixed << std::setprecision(2);  // <--- Only needs done once. I usually put this at the top.

    cout <<
        "\n"
        " What would you like to buy?\n"
        "   1. Bread:\n"
        "   2. Milk:\n"
        "   3. Soap:\n"
        "   4. Eggs:\n"
        "   5. Deodorant:\n"
        "   6. Juice:\n"
        "   7. Chips:\n"
        "   8. Forks:\n"
        "   9. Spoons:\n"
        "  10. Cups:\n";
                          // <--- Consider 11 Exit.

    while (std::cout << "  Please enter your choice: " && !(cin >> input) || input < MINCHOICE || input > MAXCHOICE)  // getting user input
    {
        if (!std::cin)
        {
            std::cerr << "\n     Invalid input!\n\n";

            std::cin.clear();
            std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');  // <--- Requires header file <limits>.
        }
        else if (input < MINCHOICE || input > MAXCHOICE)
        {
            cerr << "\n     Sorry, " << input << " wasn't a valid choice\n\n";
        }
    }

    //{  // <--- You do not need the {}s.
    if (input == 1)
    {
    product = "Bread";
    }
    else if (input == 2)
    {
    product = "Milk";
    }
    else if (input == 3)
    {
    product = "Soap";
    }
    else if (input == 4)
    {
    product = "Eggs";
    }
    else if (input == 5)
    {
    product = "Deodorant";
    }
    else if (input == 6)
    {
    product = "Juice";
    }
    else if (input == 7)
    {
    product = "Chips";
    }
    else if (input == 8)
    {
    product = "Forks";
    }
    else if (input == 9)
    {
    product = "Spoons";
    }
    else if (input == 10)
    {
    product = "Cups";
    }

    if (product != "")
    {
        double price; // To store price of product
        int age; // to store age of customer

        cout << "Please enter price for " << product << ": $"; // Asking the user for price
        cin >> price;

        cout << "Please enter your age: "; // Asking the user for age
        cin >> age;

        double tax = 0;

        if (product == "Soap", "Deodorant") // If product is not grocery
        {
            tax = 0.08 * price; // Calculating tax
        }

        double discount = 0;

        if (age >= 60) // If age is greater than 60
        {
            discount = 0.05 * price; // Calculating discount
        }

        cout << "Invoice " << endl;
        cout << "-----------" << endl;
        cout << product << " price: $" << fixed << setprecision(2) << price << endl;
        cout << "Tax: $" << fixed << setprecision(2) << tax << endl;

        if (discount > 0)  // If discount greater than 0 
        {
            cout << "Discount: $-" << fixed << setprecision(2) << discount << endl;
        }

        double total = price + tax - discount; // Calculating total price

        cout << "Total: $" << fixed << setprecision(2) << total << endl; // Displaying total price
    }
    //}
}

This is a start.

There are some other things I have noticed. I am think of something like constexpr double SALESTAX{ 0.08 };. You are letting the user enter a price. This should be part of the program and just used. That would be line 11.

I was wondering if you have learned about "switch/case" yet?

Your program only runs once allowing only 1 item to be chosen. Eventually this would be better in a loop allowing multiple choices.

Prefer using "double"s over "floats" These days a number like "0.08" is considered a double and trying to stuff that, or a calculation, into a float will have data loss.

Another thing is to prefer using the new line, (\n), over "endl". "endl" is a function that takes time to process. The more you have the longer it takes the program to run.

Line 19 demonstrates that you do not need a "cout" for every line. In this case what looks like 12 individual strings is considered 1 big string by the IDE and compiler. One advantage is that it looks more like what will be displayed on the screen, so you have a better idea of what it will look like.

The biggest change starts at line 33. This is designed to check for a non numeric input and out of the valid range.

See what you think.

Andy