Loops

Lumen provides two primary loop constructs: while loops for condition-based iteration, and repeat loops for fixed-count iteration.

While Loop

A while loop repeats a block as long as a condition is true:

i = 0

while i < 10
    println i
    i = i + 1
endwhile

• The condition is checked at the start of each iteration.
• The loop exits when the condition becomes false.
• If the condition is false initially, the loop body never executes.

Repeat Loop

A repeat loop repeats a block a fixed number of times:

repeat 5
    println 'Hello'
endrepeat

Repeat with Iterator

Use the optional iterator syntax to automatically manage a loop variable:

repeat 5, i
    println i
endrepeat

This prints 0 1 2 3 4 (the iterator starts at 0 and increments each iteration).

The iterator is equivalent to:

i = 0
repeat 5
    println i
    i = i + 1
endrepeat

Loop Control

Break

Use break to exit a loop early:

i = 0

while i < 100
    if i == 5
        break
    endif
    println i
    i = i + 1
endwhile

Continue

Use continue to skip to the next iteration:

repeat 10, i
    if i % 2 == 0
        continue
    endif
    println i
endrepeat

This prints only the odd numbers from 0 to 9.

Combining Loops and Conditionals

Loops and conditionals work seamlessly together. Here’s FizzBuzz using a repeat loop with inline condition expressions:

repeat 15, i
    if i % 15 == 0
        println 'FizzBuzz'
    elif i % 3 == 0
        println 'Fizz'
    elif i % 5 == 0
        println 'Buzz'
    else
        println i
    endif
endrepeat

See Conditionals for more details on if, elif, and else.

Legacy: Labels and Jumps

Before loops were added to Lumen, iteration was handled with labels and jumps. This approach is still supported but while and repeat loops are preferred:

i = 0

label loop

println i

i = i + 1

if i < 10
    jump loop
endif

See Labels & Jumps for more details.