Decisions with if

An if statement chooses whether a block of code should run:

if temperature > 30 then
    print("It is hot")
end

The condition between if and then must have type Boolean. Pop does not treat numbers, strings, objects, or nil as truthy or falsy values.

Choosing between two paths

Add else when the program should run another block if the condition is false:

if score > 9 then
    print("New high score")
else
    print("Keep trying")
end

Exactly one branch runs. Both finish at the shared end.

Testing several cases

Use elseif to test more conditions without extra nesting:

if score > 89 then
    print("Excellent")
elseif score > 59 then
    print("Passed")
else
    print("Try again")
end

Conditions are checked from top to bottom, stop after the first true condition, and share one final end. Each branch has its own scope.

See Elseif chains for evaluation order, scopes, and a complete classification example.

Choosing a value

An if expression selects between two values:

local label = if score > 59 then "passed" else "try again"

It requires else, has no trailing end, and evaluates exactly one branch. Both branch values must have the same static type. Pop does not use ?: punctuation or invent a union for unlike branches.

Names declared in branches

Each branch is a scope. A local declared inside it is available only until that branch ends:

if authenticated then
    local message = "Welcome back"
    print(message)
end

-- message is no longer in scope

When the branches only choose one value, prefer an if expression. Use a statement when branches perform several operations or return early.