I'm learning programming in ML (OCaml), and earlier I asked about ML functions of type
'a -> 'b. Now I've been experimenting a bit with functions of type
'a list -> 'b list. There are some obvious simple examples:
let rec loop l = loop l let return_empty l =  let rec loop_if_not_empty = function  ->  | l -> loop_if_not_empty l
What I can't figure out is how to make a function that does something other than return the empty list or loop (without using any library function). Can this be done? Is there a way to return non-empty lists?
Edit: Yes, if I have a function of type
'a -> 'b, then I can make another one, or a function of type
'a list -> 'b list, but what I'm wondering here is how to make the first one.