Reorganize the library for better backend flexibility.

src/core.ml

@@ -0,0 +1,19 @@
+
+type ('a, 'b) conv = {
+  to_ : 'a -> 'b ;
+  from_ : 'b -> 'a ;
+}
+
+module Seq = struct
+  include Seq
+
+  let of_list l =
+    let rec aux l () = match l with
+      | [] -> Seq.Nil
+      | x :: tail -> Seq.Cons (x, aux tail)
+    in
+    aux l
+  let to_rev_list gen =
+    fold_left (fun acc x -> x :: acc) [] gen
+  let to_list gen = List.rev (to_rev_list gen)
+end

src/dune

@@ -3,5 +3,15 @@
  (public_name tyre)
  (synopsis
    "Tyre is a set of combinators to build type-safe regular expressions")
- (libraries re result seq)
+ (libraries re tyrefun)
+ (modules Tyre Impl)
  (ocamlopt_flags :standard -O3))
+
+(library
+ (name        tyrefun)
+ (public_name tyre.fun)
+ (libraries result seq)
+ (modules_without_implementation sigs)
+ (modules Tyrefun Core Functor Sigs)
+ (ocamlopt_flags :standard -O3)
+)