mapWithPrevious.kt

inline fun <T, R> Iterable<T>.mapWithPrevious(transform: (previous: R?, it: T) -> R): List<R> {
    var previous: R? = null
    return this.map { it ->
        val transformed = transform(previous, it)
        previous = transformed
        transformed
    }
}

val mapped = someCollection.mapWithPrevious { previousTransformation, it -> 
               if (previousTransformation !=null) {
                  // Use data from the previous transformation?
                  SomeClass(12345,previousTransformation.balance)
               } else {
                  SomeClass(12345, 0.00) 
               }
             }