Conditionals in Lua

Conditional statements allow your program to make decisions and execute different code based on conditions. They're essential for creating dynamic, responsive programs. Lua provides if, elseif, and else statements for controlling program flow. Let's learn how to use them effectively!

The if Statement

The simplest conditional statement checks if a condition is true:

local age = 18

if age >= 18 then
    print("You are an adult")
end

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The if-else Statement

Use else to execute code when the condition is false:

local temperature = 25

if temperature > 30 then
    print("It's hot!")
else
    print("It's not too hot")
end

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The if-elseif-else Statement

Use elseif to check multiple conditions:

local score = 85

if score >= 90 then
    print("Grade: A")
elseif score >= 80 then
    print("Grade: B")
elseif score >= 70 then
    print("Grade: C")
elseif score >= 60 then
    print("Grade: D")
else
    print("Grade: F")
end

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Truthiness in Lua

In Lua, only false and nil are considered false. Everything else is true!

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Nested Conditionals

You can nest if statements inside each other:

local age = 25
local hasLicense = true

if age >= 18 then
    if hasLicense then
        print("You can drive")
    else
        print("You need a license")
    end
else
    print("You're too young to drive")
end

if age >= 18 and hasLicense then
    print("You can drive")
end

Combining Conditions

Use logical operators to create complex conditions:

AND Operator

local age = 25
local hasTicket = true

if age >= 18 and hasTicket then
    print("You can enter the concert")
end

OR Operator

local isWeekend = true
local isHoliday = false

if isWeekend or isHoliday then
    print("No work today!")
end

NOT Operator

local isRaining = false

if not isRaining then
    print("Let's go outside!")
end

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Ternary-like Pattern

Lua doesn't have a ternary operator, but you can use and/or:

-- Pattern: condition and trueValue or falseValue
local age = 20
local status = age >= 18 and "adult" or "minor"
print(status)  -- "adult"

-- Traditional if-else equivalent:
local status
if age >= 18 then
    status = "adult"
else
    status = "minor"
end

Common Patterns

Checking for nil

local value = getUserInput()

if value then
    print("Got value:", value)
else
    print("No value provided")
end

Default Values

local function greet(name)
    name = name or "Guest"  -- Default to "Guest" if nil
    print("Hello, " .. name)
end

greet()         -- Hello, Guest
greet("Alice")  -- Hello, Alice

Range Checking

local score = 85

if score >= 0 and score <= 100 then
    print("Valid score")
else
    print("Invalid score")
end

Practice Exercise

Try these conditional challenges:

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Summary

What's Next?

Now that you can make decisions in your code, it's time to learn about loops! In the next lesson, we'll explore how to repeat code with while, repeat, and for loops. Let's continue! 🚀