fun <T> verified(input : T, error : String, expression : (T) -> Boolean) = Verified(input, error, expression)


class Verified<T>(private var value : T, private val error : String, private val expression : (T) -> Boolean) : ReadWriteProperty<Any, T> {

    init {
        require(expression(value)) { error }
    }

    override fun getValue(thisRef : Any, property : KProperty<*>) : T = value

    override fun setValue(thisRef : Any, property : KProperty<*>, value : T) {
        require(expression(value)) { error }
        this.value = value
    }

}