Understanding While Loops

So far, you have learned how to use for loops in Lua to repeat actions a set number of times or to process each item in a list. You have also discovered how to control these loops with the break statement, allowing you to exit early when needed. Now, let's explore a new kind of loop: the while loop.

The while loop is perfect for situations where you do not know in advance how many times you need to repeat an action. Instead of counting or looping through a list, a while loop keeps running as long as a certain condition is true. This gives you more flexibility and control over your program's flow.

In this lesson, you will learn how to use the while loop to solve problems where the number of repetitions depends on changing conditions. For example, imagine you are planning a trip and want to add countries to your itinerary until your budget runs out. You do not know exactly how many countries you can afford, so a while loop is the right tool for the job.

Here is a sample code snippet to show how this works:

local travel_budget = 5000
local country_costs = {France = 1000, Italy = 800, Spain = 900, Japan = 1200}
local countries_to_consider = {"Japan", "France", "Spain", "Italy"}

local total_cost = 0
local chosen_countries = {}

local i = 1
while total_cost < travel_budget and i <= #countries_to_consider do
    local country = countries_to_consider[i]
    local cost = country_costs[country]
    if total_cost + cost <= travel_budget then
        total_cost = total_cost + cost
        table.insert(chosen_countries, country)
    end
    i = i + 1
end

print("Countries chosen for the trip: " .. table.concat(chosen_countries, ", "))

Let's break down what happens in the code above:

• travel_budget is the total amount of money you have for your trip.
• country_costs is a table that lists how much it costs to visit each country.
• countries_to_consider is the list of countries you want to visit, in order.
• total_cost keeps track of how much you have spent so far.
• chosen_countries is a list that will store the countries you can afford to visit.
• i is used to keep track of which country you are currently considering.

The while loop continues as long as you have not spent your entire budget (total_cost < travel_budget) and there are still countries left to consider (i <= #countries_to_consider). Inside the loop, the code checks if adding the next country would keep you within your budget. If it does, the country is added to your list and the total cost is updated. The loop then moves on to the next country. When the loop finishes, it prints out the list of countries you can afford to visit.

Note: Just like with for loops, you can use the break statement inside a while loop to exit the loop early when a certain condition is met. This gives you even more control over how and when your loop stops running.