ioc__strategy_pattern.kt

class Report(
    val women: List<Person>,
    val men: List<Person>
) {
    fun isEmpty(): Boolean {
        return women.isEmpty() && men.isEmpty()
    }
}

class ReportGenerator(
    private val repository: Repository
) {

    fun create(filter: (Report) -> Report): Report {
        val people = repository.fetchAllPeople()

        val rawReport = splitByGender(people)
        if (rawReport.isEmpty()) {
            return rawReport
        }

        // the filter function does not have any control over its invokation      
        val filteredReport = filter(rawReport)
        return sortByName(filteredReport)
    }

    // ...
}

// example:
val reportGenerator = ReportGenerator(repository)

val withPeopleOver21 = { rawReport: Report ->
    val over21 = { person: Person -> person.age > 21 }
    Report(
        rawReport.women.filter(over21),
        rawReport.men.filter(over21)
    )
}

val reportWithPeopleOver21 = reportGenerator.create(withPeopleOver21)