Repetition with loops

Loops run a block more than once. A while loop checks its condition before every iteration:

namespace Countdown

function main()
    local number = 3

    while number > 0 do
        print(number)
        number = number - 1
    end

    print("Go!")
end

This program prints 3, 2, 1, and then Go!. When number > 0 becomes false, execution continues after end.

Because the condition is checked first, a while body might run zero times:

local number = 0
while number > 0 do
    print(number) -- never runs
end

As with if, a loop condition must be a Boolean.

Running the body at least once

A repeat loop checks its condition after the body:

local number = 1

repeat
    print(number)
    number = number + 1
until number > 3

The body runs for 1, 2, and 3. Even when the condition is already true in principle, a repeat body always runs once before Pop checks until.

A local declared in the body remains available to the until condition, which is useful when the condition depends on work just performed:

repeat
    local next = calculateNext()
    use(next)
until finished(next)

That local is not available after the loop finishes.

This release has no implemented break or continue statement. Express early stopping through the loop condition, and place conditional work inside an if when an iteration should skip part of its body.