Add Toolbox.mli.

src/Toolbox.mli

+(* This functor is applied to a type of terms, equipped with visitor classes.
+   It produces a toolbox of useful functions that operate on terms. *)
+
+module Make (Term : ToolboxInput.INPUT) : sig
+
+  open Term
+
+  (* A raw term is one where every name is represented as a string. This form
+     is typically produced by a parser, and consumed by a printer. It is not
+     used internally. *)
+
+  type raw_term =
+    (string, string) term
+
+  (* A nominal term is one where every name is represented as an atom. Although
+     this is not visible in this type definition, we may additionally impose a
+     Global Uniqueness Hypothesis (GUH), that is, we may require every binding
+     name occurrence to carry a distinct atom. *)
+
+  type nominal_term =
+    (Atom.t, Atom.t) term
+
+  val fa_term: nominal_term -> Atom.Set.t
+  val filter_term: (Atom.t -> bool) -> nominal_term -> Atom.t option
+  val closed_term: nominal_term -> bool
+  val occurs_term: Atom.t -> nominal_term -> bool
+
+  exception IllFormed of Atom.t (* = Atom.Set.NonDisjointUnion *)
+  val ba_term: nominal_term -> Atom.Set.t
+  val ba_terms: nominal_term list -> Atom.Set.t
+  val wf_term: nominal_term -> bool
+  val wf_terms: nominal_term list -> bool
+
+  val copy_term: nominal_term -> nominal_term
+
+  val show_term: nominal_term -> raw_term
+
+  exception Unbound of string (* = KitImport.Unbound *)
+  val import_term: KitImport.env -> raw_term -> nominal_term
+
+  val export_term: KitExport.env -> nominal_term -> raw_term
+
+  val size_term: (_, _) term -> int
+
+  val equiv_term: nominal_term -> nominal_term -> bool
+
+  val subst_term_term : nominal_term Atom.Map.t -> nominal_term -> nominal_term
+  val subst_term_term1: nominal_term  -> Atom.t -> nominal_term -> nominal_term
+
+end