Cubicle 1.1.2 documentation and source : Variable.all

let rec all_permutations l1 l2 = 
  (*assert (List.length l1 <= List.length l2);*)
  match l1 with
    | [] -> [[]]
    | x::l -> cross l [] x l2
and cross l pr x st =
  match st with
    | [] -> []
    | y::p -> 
	let acc = all_permutations l (List.rev_append pr p) in
	let acc = 
	  if acc = [] then [[x,y]]
	  else List.rev_map (fun ds -> (x, y)::ds) acc in
	List.rev_append acc (cross l (y::pr) x p)