InterestCalculator.kt

interface AccountType {
    var balance: Float
    val rate: Float

    fun calculateInterest(): Float
}

interface InterestCalculator {
    fun calculateInterest(balance: Float, rate: Float): Float
}

class InterestCalculatorImpl : InterestCalculator {
    override fun calculateInterest(balance: Float, rate: Float): Float {
        return balance * rate
    }
}

class SecuritiesInterestCalculator : InterestCalculator {
    override fun calculateInterest(balance: Float, rate: Float): Float {
        return balance * rate * 1.3f
    }
}

class Stocks(delegate: AccountType, interestCalculator: InterestCalculator) : AccountType by delegate,
    InterestCalculator by interestCalculator

fun main() {
    val stocksAccount = Stocks(AccountTypeImpl(100f), SecuritiesInterestCalculator())

    println(
        with(stocksAccount) {
            "The interest of the money market account is ${calculateInterest(
                balance,
                rate
            )}" // Outputs 6.5
        }
    )
}