# Recipes

RuLa allows you to write quite complicated conditions and formulas. Here are some recipes or snippets or useful RuLa statements to use:

### Check if more information than expected is missing

Let's say we expect `first_payment_*` information to be missing in a certain step, but nothing else. Heres a recipe how to check for exactly that:

```
COUNT(
    CASE.missing_information_keys - [
        CASE.outcome_instance.first_payment_first_name.key(),
        CASE.outcome_instance.first_payment_last_name.key(),
        CASE.outcome_instance.first_payment_iban.key()
    ]
) > 0
```

We are using `CASE.missing_information_keys` for Atfinity to tell us the keys of information still needed but missing in the current case. With `INF.key()` we then compare these keys to the keys of information we expect to be missing in the case.\
Finally, we use the "infix [set difference operator](/rule-language/operators/list-operators/set_difference.md) ", the minus, to see if the list of `missing_information_keys` is empty after the remove all the known missing information and count the elements in this list.


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