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while

Use while when you want to keep looping for as long as a condition stays true.

actor main(env):
    var remaining = 3

    while remaining > 0:
        print("remaining:", remaining)
        remaining -= 1

    print("done")
    env.exit(0)

With while, make sure something in the loop body can eventually make the condition false. If that condition depends on a changing value in actor code, that value usually needs var.

while is useful when the number of iterations is not the main point. What matters is the condition.

actor main(env):
    var retries = 5

    while retries > 0:
        print("trying...")
        retries -= 1

    env.exit(0)

If you already have a collection or a simple numeric range, a for loop is usually clearer than a while loop. Reach for while when the condition really is the center of the logic.

A while loop makes state transitions explicit, which is useful for retries and actor-local state machines. The tradeoff is that you now own the loop invariant and termination condition, so it is more error-prone than for when the iteration boundary is already known.

Typical uses include retry loops, waiting for a condition to change, and small state machines where each pass updates the state before checking again.