@scruffyfox It's also worth checking out lazy `Sequence`s and the various transformation operations like

map

,

flatMap

etc I often find these easier to process than "oldschool" java loops. Just to give you an idea (completely untested and may not meet your needs):

fun searchParent(id: String): Module? =
        modules
                .asSequence()
                .mapNotNull { searchParent(it, id) }
                .firstOrNull()

fun searchParent(root: Module, id: String): Module? =
        root.steps
                ?.asSequence()
                ?.flatMap { it.steps?.asSequence() ?: emptySequence() }
                ?.firstOrNull { it.id == id }

surely with mapNotNull will iterate through every item regardless if it has found the parent or not? so would be much more inefficient than doing the original loop and returning once found? also why add

.asSequence()

,

modules

is already type

List<Module>

so surely that is redundant?

that's the thing about sequences. they're evaluated lazily.