Hi, Pascal
(and hi, list!)
1. Here is one: define a function that takes two lists, both of which have elements in growing order (i.e 1,2,3,3,5,9,9,..), and outputs a list with the type of [Either a a], where a `Left a' would represent an element from the first list, a `Right a' from the second list. Make it so that the elements are in order, and also that the lefts preceede the rights.
Example, the inputs of [1,1,3,7,7] and [1,2,3,5,5] would result in [Left 1, Left 1, Right 1, Right 2, Left 3, Right 3, Right 5, Right 5, Left 7, Left 7]
2. As an extension (not sure if this is too difficult for what you're looking for): write another function that takes a list-of-lists as input