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for Loop with a Step

Part of the Fundamentals section of Coddy's Lua journey — lesson 74 of 90.

The numeric for loop becomes even more powerful when you add a third argument called the step. The step controls how much the loop variable changes each time through the loop.

The expanded syntax looks like this:

for variable = start, finish, step do
    -- code to repeat
end

Here's an example that counts by 2s instead of 1s:

for i = 2, 10, 2 do
    print(i)
end

This loop starts at 2, goes up to 10, and increases by 2 each time, printing: 2, 4, 6, 8, 10.

You can also use negative steps to count backwards:

for i = 5, 1, -1 do
    print(i)
end

This counts down from 5 to 1, printing: 5, 4, 3, 2, 1.

The step gives you precise control over how your loop progresses, making it perfect for tasks like processing every other item in a list, creating countdowns, or working with specific number patterns.

challenge icon

Challenge

Easy

Create a multiplication table generator that uses a numeric for loop with a step to display multiples of 3. Write a for loop that starts at 3, goes up to 15, and uses a step of 3 to print only the multiples of 3.

Inside the loop, print each multiple value on a separate line. This will demonstrate how the step parameter controls the loop's progression by skipping values.

Cheat sheet

The numeric for loop can include a third argument called the step to control how much the loop variable changes each iteration:

for variable = start, finish, step do
    -- code to repeat
end

Count by 2s:

for i = 2, 10, 2 do
    print(i)  -- prints: 2, 4, 6, 8, 10
end

Count backwards with negative step:

for i = 5, 1, -1 do
    print(i)  -- prints: 5, 4, 3, 2, 1
end

Try it yourself

-- TODO: Write your code here
-- Create a for loop that starts at 3, goes up to 15, with a step of 3
-- Print each multiple on a separate line
quiz iconTest yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

The LanguageHello World!Comments

4Operators 2 Relational & Logic

Equality OperatorsRelational OperatorsThe 'and' OperatorThe 'or' OperatorThe 'not' OperatorShort-Circuit EvaluationTruthy and Falsy ValuesRecap - Simple Logic

7Basic Conditional Logic

The if-then StatementThe if-then-else StatementThe elseif StatementRecap - Treasure Chest

10Tables Part 1: List-Style

What is a Table?Creating a TableAccessing Elements by IndexModifying Elements by IndexThe Length Operator '#'table.insert()table.remove()Recap - Manage Party Members

13Project: Simple Potion Shop

Project SetupAdding a PotionProject lessonDisplaying the InventoryProject lessonCalculating Total Stock ValueProject lessonFinding a Specific PotionProject lessonSelling a PotionProject lesson

2Variables and Data Types

What is a Variable?NumbersStringsBooleansThe Value 'nil'The type() FunctionNaming ConventionsRecap - Character Profile

5Basic Output

Printing LiteralsPrinting VariablesPrinting Multiple ValuesCombining Strings & VariablesThe tostring() FunctionInputCastRecap - Status ReportRecap - Till 120

8String Manipulation Basics

string.len()string.upper & string.lowerstring.sub()string.rep()string.find()Recap - Format Username

11Tables 2: Dictionary-Style

Key-Value PairsCreating Dictionary-Style TablAccessing - Bracket NotationAccessing with Dot NotationAdding and Modifying PairsRemoving Pairs with nilRecap - Item Properties

14Variable Scope

Global VariablesLocal VariablesWhy Use Local Variables?Scope and BlocksRecap - Scope Puzzle

3Operators 1 Arithmetic & Conc

Arithmetic OperatorsModulo OperatorExponentiation OperatorString ConcatenationOperator PrecedenceRecap - Simple Calculations

6Project: Character Stats Disp

Welcome MessageDeclare Character StatsProject lessonDisplay Basic StatsProject lessonAdd a Boolean FlagProject lessonFinal SummaryProject lesson

9Functions Basics

Declaring a FunctionCalling a FunctionFunctions with ParametersFunctions with Multiple ParamsThe 'return' StatementRecap - Area Calculator

12Loops Basics

The while LoopThe repeat-until LoopThe Numeric for Loopfor Loop with a StepThe 'break' StatementRecap - Countdown

15Final Challenges

Recap - Player TurnRecap - Simple DatabaseRecap - Sum of Even Numbers