Transfer practice · shipping(total) returns 0 at totals of 30 or above and 4 below 30. Include the exact free-shipping boundary.

Return a usable price: practice

v3 · Activity 1 of 1 · return-values · early-return · 9 min Runs here

Chapter outline

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Mini-mission

Use a familiar idea in a different task. Read the changed requirement before running.

Your task

shipping(total) returns 0 at totals of 30 or above and 4 below 30. Include the exact free-shipping boundary.

Interface: price(quantity, unitPrice) -> number

Input	Expected
Below threshold`29`	`4`
Boundary`30`	`0`
Above`42`	`0`

See another example

local function points(count)
    if count < 0 then return 0 end
    return count * 5
end
local total = points(3) + 2
print(total)
return points

points returns 15, allowing the caller to add 2. Merely printing 15 would not supply that value to +.

Syntax in this activity

New syntax: early return, negative numbers

Earlier ideas used here

functions
parameters
return-values
comparison
if-else

Explain more

print exposes a value to a person; return gives it to the caller. A function without a returned value supplies nil.

return also stops the current function call. A guard at the top can reject a bad input before the main calculation.

Our rule treats a negative quantity as invalid and returns 0. This is an exercise policy, not a complete store security design.

Explain this code

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

  pricequantity, unitPrice
     quantity  0 
        0
    
    quantity  unitPrice

 price

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 points(count)
    if count < 0 then return 0 end
    return count * 5
end
local total = points(3) + 2
print(total)
return points

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 shipping(total)
    print(4)
end
return shipping

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

Your output will appear here.

Ready

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Your task

shipping(total) returns 0 at totals of 30 or above and 4 below 30. Include the exact free-shipping boundary.

Interface: price(quantity, unitPrice) -> number

Input	Expected
Below threshold`29`	`4`
Boundary`30`	`0`
Above`42`	`0`

See another example

local function points(count)
    if count < 0 then return 0 end
    return count * 5
end
local total = points(3) + 2
print(total)
return points

points returns 15, allowing the caller to add 2. Merely printing 15 would not supply that value to +.

Syntax in this activity

New syntax: early return, negative numbers

Earlier ideas used here

functions
parameters
return-values
comparison
if-else

Explain more

print exposes a value to a person; return gives it to the caller. A function without a returned value supplies nil.

return also stops the current function call. A guard at the top can reject a bad input before the main calculation.

Our rule treats a negative quantity as invalid and returns 0. This is an exercise policy, not a complete store security design.

Explain this code

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

  pricequantity, unitPrice
     quantity  0 
        0
    
    quantity  unitPrice

 price

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 points(count)
    if count < 0 then return 0 end
    return count * 5
end
local total = points(3) + 2
print(total)
return points

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

Experiment Output

Your output will appear here.