Control flow

Control flow decides which code runs, when it runs, and how often it runs.

Acton does not have a Rust-style match expression. Use if/elif/else for branching, and combine that with optionals or exceptions when the question is about absence or failure.

Start with these three everyday tools:

if / elif / else for branching
for for iterating over items
while for repeating while a condition stays true

Loops also support a few extra tools:

break to stop the loop early
continue to skip to the next iteration
else to run code after a loop finishes normally, without a break

If you are new to programming, start with if, for, and while and treat loop else as optional. Most code uses the first three tools far more often.

for n in range(5):
    if n == 2:
        continue
    if n == 4:
        break
    print(n)
else:
    print("finished without break")

Loop else is tied to break, not to "zero iterations". It runs whenever the loop finishes normally, which makes it useful for search-style logic but easy to misread if used casually.

Acton also has actor-specific control patterns such as after. Those matter once you start thinking about actors, timers, and concurrency.

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Control flow