Labels & Jumps

Lumen has no dedicated loop keywords (while, for) — loops are built from label and jump, the same primitives the underlying bytecode exposes directly.

Unconditional jump

label repeat
println 'Hello, world!'
jump repeat

label <name> marks a position in the program. jump <name> transfers control to it unconditionally. The pair above is an infinite loop — see the Labels & Jumps Demo example.

Conditional jump

Combine jump with an if block to build a real loop with an exit condition:

i = 0

label loop

println i

i = i + 1

if i < 10
    jump loop
endif

This counts from 0 to 9. The loop body runs, i increments, and the if decides whether to jump back to label loop or fall through and end the program.

Scope

Labels are program-global — a jump can target any label in the file, not just ones in the same block. This is what makes them powerful (and occasionally easy to misuse): there’s no structural nesting enforced between a label and the jumps that target it, unlike if/endif or routine/endroutine.