Concatenate lists in constant time in scala?

Question

In Scala, is there a built-in function or external library for concatenating two lists (or arrays, or vectors, or listbuffers, etc) in constant time? Such an operation would presumably destroy / mutate the two original lists. All the functions I see for concatenating lists run in linear time, as far as I can tell.

Thanks much.

Answer 1

There is the UnrolledBuffer which has the concat method taking another UnrolledBuffer and returning their concatenation in O(1). It is destructive to the argument buffer - the second buffer will be empty after this calling this method.