diff --git a/sledge/src/fol/context.ml b/sledge/src/fol/context.ml
index 27a3d321d..44d99c6ec 100644
--- a/sledge/src/fol/context.ml
+++ b/sledge/src/fol/context.ml
@@ -32,7 +32,7 @@ let uninterpreted e = equal_kind (classify e) Uninterpreted
 
 let rec max_solvables e =
   if non_interpreted e then Iter.return e
-  else Iter.flat_map ~f:max_solvables (Trm.subtrms e)
+  else Iter.flat_map ~f:max_solvables (Trm.trms e)
 
 let fold_max_solvables e s ~f = Iter.fold ~f (max_solvables e) s
 
@@ -168,8 +168,8 @@ end = struct
     in
     ( is_var_in xs e
     || is_var_in xs f
-    || (uninterpreted e && Iter.exists ~f:(is_var_in xs) (Trm.subtrms e))
-    || (uninterpreted f && Iter.exists ~f:(is_var_in xs) (Trm.subtrms f)) )
+    || (uninterpreted e && Iter.exists ~f:(is_var_in xs) (Trm.trms e))
+    || (uninterpreted f && Iter.exists ~f:(is_var_in xs) (Trm.trms f)) )
     $> fun b ->
     [%Trace.info
       "is_valid_eq %a%a=%a = %b" Var.Set.pp_xs xs Trm.pp e Trm.pp f b]
@@ -457,7 +457,7 @@ let pre_invariant r =
       (* no interpreted terms in carrier *)
       assert (non_interpreted trm || fail "non-interp %a" Trm.pp trm ()) ;
       (* carrier is closed under subterms *)
-      Iter.iter (Trm.subtrms trm) ~f:(fun subtrm ->
+      Iter.iter (Trm.trms trm) ~f:(fun subtrm ->
           assert (
             (not (non_interpreted subtrm))
             || (match subtrm with Z _ | Q _ -> true | _ -> false)
@@ -525,12 +525,12 @@ let rec extend_ a r =
   match (a : Trm.t) with
   | Z _ | Q _ -> r
   | _ -> (
-      if interpreted a then Iter.fold ~f:extend_ (Trm.subtrms a) r
+      if interpreted a then Iter.fold ~f:extend_ (Trm.trms a) r
       else
         (* add uninterpreted terms *)
         match Subst.extend a r with
         (* and their subterms if newly added *)
-        | Some r -> Iter.fold ~f:extend_ (Trm.subtrms a) r
+        | Some r -> Iter.fold ~f:extend_ (Trm.trms a) r
         | None -> r )
 
 (** add a term to the carrier *)
@@ -640,10 +640,10 @@ let ppx_diff var_strength fs parent_ctx fml ctx =
 let fold_uses_of r t s ~f =
   let rec fold_ e s ~f =
     let s =
-      Iter.fold (Trm.subtrms e) s ~f:(fun sub s ->
+      Iter.fold (Trm.trms e) s ~f:(fun sub s ->
           if Trm.equal t sub then f s e else s )
     in
-    if interpreted e then Iter.fold ~f:(fold_ ~f) (Trm.subtrms e) s else s
+    if interpreted e then Iter.fold ~f:(fold_ ~f) (Trm.trms e) s else s
   in
   Subst.fold r.rep s ~f:(fun ~key:trm ~data:rep s ->
       fold_ ~f trm (fold_ ~f rep s) )
diff --git a/sledge/src/fol/exp.ml b/sledge/src/fol/exp.ml
index a2bc3dde5..81f857f11 100644
--- a/sledge/src/fol/exp.ml
+++ b/sledge/src/fol/exp.ml
@@ -259,20 +259,16 @@ module Term = struct
 
   (** Traverse *)
 
-  let rec iter_vars_c c ~f =
-    match c with
-    | `Ite (cnd, thn, els) ->
-        Iter.iter ~f (Fml.vars cnd) ;
-        iter_vars_c ~f thn ;
-        iter_vars_c ~f els
-    | `Trm t -> Iter.iter ~f (Trm.vars t)
-
-  let iter_vars e ~f =
-    match e with
-    | `Fml p -> Iter.iter ~f (Fml.vars p)
-    | #cnd as c -> iter_vars_c ~f c
+  let iter e ~f:iter_t =
+    let iter_f f = Iter.flat_map ~f:iter_t (Fml.trms f) in
+    let rec iter_c = function
+      | `Ite (cnd, thn, els) ->
+          Iter.(append (iter_f cnd) (append (iter_c thn) (iter_c els)))
+      | `Trm e -> iter_t e
+    in
+    match e with `Fml f -> iter_f f | #cnd as c -> iter_c c
 
-  let vars e = Iter.from_labelled_iter (iter_vars e)
+  let vars = iter ~f:Trm.vars
 
   (** Transform *)
 
diff --git a/sledge/src/fol/fml.mli b/sledge/src/fol/fml.mli
index d5f85d345..a5c281f90 100644
--- a/sledge/src/fol/fml.mli
+++ b/sledge/src/fol/fml.mli
@@ -83,6 +83,7 @@ val fold_dnf :
   -> 'disjunction
 
 val vars : t -> Var.t iter
+val trms : t -> Trm.t iter
 
 (** Query *)
 
diff --git a/sledge/src/fol/trm.ml b/sledge/src/fol/trm.ml
index f39d98eb0..29f17f921 100644
--- a/sledge/src/fol/trm.ml
+++ b/sledge/src/fol/trm.ml
@@ -428,23 +428,16 @@ let map e ~f =
 
 (** Traverse *)
 
-let iter_subtrms e ~f =
-  match e with
-  | Var _ | Z _ | Q _ -> ()
-  | Arith a -> Iter.iter ~f (Arith.trms a)
-  | Splat x -> f x
-  | Sized {seq= x; siz= y} ->
-      f x ;
-      f y
+let trms = function
+  | Var _ | Z _ | Q _ -> Iter.empty
+  | Arith a -> Arith.trms a
+  | Splat x -> Iter.(cons x empty)
+  | Sized {seq= x; siz= y} -> Iter.(cons x (cons y empty))
   | Extract {seq= x; off= y; len= z} ->
-      f x ;
-      f y ;
-      f z
-  | Concat xs | Apply (_, xs) -> Array.iter ~f xs
-
-let subtrms e = Iter.from_labelled_iter (iter_subtrms e)
+      Iter.(cons x (cons y (cons z empty)))
+  | Concat xs | Apply (_, xs) -> Iter.of_array xs
 
 (** Query *)
 
 let fv e = Var.Set.of_iter (vars e)
-let rec height e = 1 + Iter.fold ~f:(fun x -> max (height x)) (subtrms e) 0
+let rec height e = 1 + Iter.fold ~f:(fun x -> max (height x)) (trms e) 0
diff --git a/sledge/src/fol/trm.mli b/sledge/src/fol/trm.mli
index 1ed83df66..14a0dbe9b 100644
--- a/sledge/src/fol/trm.mli
+++ b/sledge/src/fol/trm.mli
@@ -94,5 +94,8 @@ val height : t -> int
 
 (** Traverse *)
 
+val trms : t -> t iter
+(** The immediate subterms of a term. *)
+
 val vars : t -> Var.t iter
-val subtrms : t -> t iter
+(** The variables that occur in a term. *)