Keep deliberate false settings

v3 · Activity 10 of 12 · truthiness · nil · defaults · 9 min Runs here

Chapter outline

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One step at a time

In a condition, only false and nil count as falsey. Zero and the empty string are truthy. Luau does not treat zero as automatically false.

value or default returns one of its operands; it is not always a boolean. This shortcut replaces both nil and false, which may be wrong for settings.

Your task

soundEnabled(value) should return true when value is missing and otherwise preserve the supplied boolean. Replace the shortcut that loses false. Keep the final return shown in the starter so the checker can call or inspect your result.

Interface: soundEnabled(value) -> boolean; nil input uses true.

Input	Expected
Missing preference`nil`	`true`
Deliberately off`false`	`false`
On`true`	`true`

See another example

local function volumeOrDefault(volume)
    if volume == nil then
        return 50
    end
    return volume
end
return volumeOrDefault

Missing volume becomes 50, but volume 0 stays 0 because zero is not missing.

Syntax in this activity

New syntax: value == nil, value or default

Earlier ideas used here

booleans
comparison
functions
parameters
return-values

Explain more

In a condition, only false and nil count as falsey. Zero and the empty string are truthy. Luau does not treat zero as automatically false.

value or default returns one of its operands; it is not always a boolean. This shortcut replaces both nil and false, which may be wrong for settings.

Use value == nil when absence is the specific condition you care about. Preserve false as a deliberate setting.

Explain this code

Select a word or symbol in this authored example. Your editor draft stays unchanged.

  soundEnabledvalue
     value  

 soundEnabled

Choose a highlighted part to see what it means.

Free experiment

This is a private experiment copy. It does not replace your answer or complete the activity.

These inputs apply when your scratchpad returns the function described by the activity interface.

Test different inputs

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local function volumeOrDefault(volume)
    if volume == nil then
        return 50
    end
    return volume
end
return volumeOrDefault

Luau keyword highlighting · Ctrl/⌘ + Enter: Run · Esc: leave editorTab inserts indentation

Experiment Output

Your output will appear here.

Reset starter

Replace this code with the starter? Download your draft to keep a copy.

Code

Luau

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local function soundEnabled(value)
    return value or true
end
return soundEnabled

Luau keyword highlighting · Ctrl/⌘ + Enter: Run · Esc: leave editorTab inserts indentation

Your output will appear here.

Ready

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Your task

Interface: soundEnabled(value) -> boolean; nil input uses true.

Input	Expected
Missing preference`nil`	`true`
Deliberately off`false`	`false`
On`true`	`true`

See another example

local function volumeOrDefault(volume)
    if volume == nil then
        return 50
    end
    return volume
end
return volumeOrDefault

Missing volume becomes 50, but volume 0 stays 0 because zero is not missing.

Syntax in this activity

New syntax: value == nil, value or default

Earlier ideas used here

booleans
comparison
functions
parameters
return-values

Explain more

In a condition, only false and nil count as falsey. Zero and the empty string are truthy. Luau does not treat zero as automatically false.

value or default returns one of its operands; it is not always a boolean. This shortcut replaces both nil and false, which may be wrong for settings.

Use value == nil when absence is the specific condition you care about. Preserve false as a deliberate setting.

Explain this code

Select a word or symbol in this authored example. Your editor draft stays unchanged.

  soundEnabledvalue
     value  

 soundEnabled

Choose a highlighted part to see what it means.

Free experiment

This is a private experiment copy. It does not replace your answer or complete the activity.

These inputs apply when your scratchpad returns the function described by the activity interface.

Test different inputs

Font size Plain text

local function volumeOrDefault(volume)
    if volume == nil then
        return 50
    end
    return volume
end
return volumeOrDefault

Luau keyword highlighting · Ctrl/⌘ + Enter: Run · Esc: leave editorTab inserts indentation

Experiment Output

Your output will appear here.