The Project | About Us | Contribute | Donations | License
HOME My courses Completed
◄ Previous
◄

Loops

Next ►
►

In programming, loops are used to execute a block of code repeatedly until a specified condition is met. Lua supports several types of loops, each suited for different scenarios. In this section, we will cover the following types of loops:

  1. while loop
  2. repeat...until loop
  3. for loop

  1. while Loop

The while loop repeats a block of code as long as a specified condition is true.

Syntax

while condition do
    -- code to be executed
end

Example

local count = 1

while count <= 5 do
    print("Count is: " .. count)
    count = count + 1
end

Explanation

  • Initialization: local count = 1 initializes the variable count to 1.
  • Condition: count <= 5 is the condition that is checked before each iteration.
  • Body: print("Count is: " .. count) and count = count + 1 are executed as long as the condition is true.

  1. repeat...until Loop

The repeat...until loop is similar to the while loop, but the condition is checked after the loop body is executed. This means the loop body is always executed at least once.

Syntax

repeat
    -- code to be executed
until condition

Example

local count = 1

repeat
    print("Count is: " .. count)
    count = count + 1
until count > 5

Explanation

  • Initialization: local count = 1 initializes the variable count to 1.
  • Body: print("Count is: " .. count) and count = count + 1 are executed.
  • Condition: count > 5 is checked after the loop body is executed.

  1. for Loop

The for loop is used to iterate over a range of values or elements in a table.

Numeric for Loop

The numeric for loop iterates over a range of numbers.

Syntax

for var = start, stop, step do
    -- code to be executed
end

Example

for i = 1, 5 do
    print("i is: " .. i)
end

Explanation

  • Initialization: i = 1 initializes the variable i to 1.
  • Condition: i <= 5 is the implicit condition.
  • Step: i = i + 1 is the implicit step.

Generic for Loop

The generic for loop is used to iterate over elements in a table.

Syntax

for key, value in pairs(table) do
    -- code to be executed
end

Example

local fruits = {apple = "red", banana = "yellow", grape = "purple"}

for fruit, color in pairs(fruits) do
    print(fruit .. " is " .. color)
end

Explanation

  • Initialization: local fruits = {apple = "red", banana = "yellow", grape = "purple"} initializes the table fruits.
  • Iteration: for fruit, color in pairs(fruits) iterates over each key-value pair in the table.

Practical Exercises

Exercise 1: Sum of Numbers

Write a Lua script that calculates the sum of numbers from 1 to 10 using a while loop.

Solution

local sum = 0
local i = 1

while i <= 10 do
    sum = sum + i
    i = i + 1
end

print("Sum is: " .. sum)

Exercise 2: Factorial Calculation

Write a Lua script that calculates the factorial of a given number using a for loop.

Solution

local number = 5
local factorial = 1

for i = 1, number do
    factorial = factorial * i
end

print("Factorial of " .. number .. " is: " .. factorial)

Exercise 3: Table Iteration

Write a Lua script that prints all the elements in a table using a for loop.

Solution

local colors = {"red", "green", "blue"}

for index, color in ipairs(colors) do
    print("Color at index " .. index .. " is " .. color)
end

Common Mistakes and Tips

  • Off-by-One Errors: Ensure that your loop conditions and steps are correctly set to avoid off-by-one errors.
  • Infinite Loops: Be cautious with while and repeat...until loops to ensure that the condition will eventually become false.
  • Table Iteration: Use pairs for tables with non-numeric keys and ipairs for tables with numeric keys.

Conclusion

In this section, we covered the different types of loops in Lua: while, repeat...until, and for loops. We also provided practical examples and exercises to help you understand how to use loops effectively. Understanding loops is crucial for controlling the flow of your programs and performing repetitive tasks efficiently. In the next section, we will explore functions in Lua, which will further enhance your ability to write modular and reusable code.

◄ Previous
◄
Next ►
►
The Project | About Us | Contribute | Donations | License
© Copyright 2024. All rights reserved