How to merge tuples by same elements in Scala

Question

For example, if I have the following tuples:

(1, "a", "l")
(1, "a", "m")
(1, "a", "n")

I want to merge them like this:

(1, "a", List("l", "m", "n"))

In my case, the lists are a result from an inner join using Slick. So, the first and second elements (1 and "a") should be the same. If somebody knows how to merge like that in case of using Slick, let me know please.

Or more generally, the way to merge tuples with inner lists by the same elements.

(1, "a", "l")
(1, "a", "m")
(1, "b", "n")
(1, "b", "o")
// to like this
List( (1, "a", List("l", "m")), (1, "b", List("n", "o")) )

Answer 1

How about:

val l = ??? // Your list

val groups = l groupBy { case (a, b, c) => (a,b) }

val tups = groups map { case ((a,b), l) => (a,b,l.map(_._3)) }

tups.toList