effect.recursive_action

An action calls itself, or calls other actions that end up calling it again.

Area 3, Logic; not declinable; the next step is usually the human's.

Why Jadpo refuses it

Only functions may call themselves. A function only works out a value, so calling itself again is how it walks a thread of replies or counts down. An action reads and changes stored data and calls outside services, and each pass round a cycle does all of that again, with nothing in the data saying how many times. A cycle with no end never finishes.

Jadpo won't choose the fix for you, because the two fixes do different things: one keeps the repeated work but takes the effects out of it, and the other runs the effects once for each item of a list you give.

What it looks like

main.jadpo:

type Count = Int {    min: 0}action ping(count: Count) -> Unit {    pong(count)}action pong(count: Count) -> Unit {    ping(count)}

   |10 |     ping(count)   |     ^^^^ calls back round

(human) at the end of the next: line tells your coding agent to stop and ask you which fix you want, because the choice is yours to make: it decides how many times the action's reads and writes happen.

The error is at the call that closes the cycle. An action that calls itself directly is reported the same way, as "Action ping calls itself".

How to fix it

The question is what repeats: working out a value, or the action's effects.

If what repeats is working out a value, move it into a function, which may call itself. Here countdown steps down to zero, and ping calls it once:

function countdown(count: Count) -> Count {    if (count == 0) {        return 0    }    return countdown(Count(count - 1))}

The action's effects now happen once, and only the function repeats. pong no longer calls ping, so there is no cycle. How deep a function can call itself is limited while the app runs (Recursion).

If the action should run once for each item, give it the list and loop over it with for:

action ping(counts: List<Count>) -> Unit {    for count in counts {        pong(count)    }}

pong runs once for each count in the list, so the list's length says how many times. A call that leaves your app, such as a provider operation, still can't be made in the loop's body (No outside calls inside a loop).

Related

• Recursion
• Functions and actions
• Loops