diff --git a/bench/bro-tree.sml b/bench/bro-tree.sml
index 1ee8a8a..7306e36 100644
--- a/bench/bro-tree.sml
+++ b/bench/bro-tree.sml
@@ -54,4 +54,14 @@ struct
 
   fun insert (str, tree) =
     insRoot (ins (str, tree))
+
+  fun exists (str, tree) =
+    case tree of
+      N0 => false
+    | N1 t => exists (str, t)
+    | N2 (l, k, r) =>
+        if str < k then exists (str, l)
+        else if str > k then exists (str, r)
+        else true
+    | _ => raise Match
 end
diff --git a/bench/build-exists-bro-tree b/bench/build-exists-bro-tree
new file mode 100755
index 0000000..dbabc3e
Binary files /dev/null and b/bench/build-exists-bro-tree differ
diff --git a/bench/build-exists-bro-tree.mlb b/bench/build-exists-bro-tree.mlb
new file mode 100644
index 0000000..1d82d8a
--- /dev/null
+++ b/bench/build-exists-bro-tree.mlb
@@ -0,0 +1,10 @@
+$(SML_LIB)/basis/basis.mlb
+
+ann
+  "allowVectorExps true"
+in
+  words.sml
+end
+
+bro-tree.sml
+build-exists-bro-tree.sml
diff --git a/bench/build-exists-bro-tree.sml b/bench/build-exists-bro-tree.sml
new file mode 100644
index 0000000..8a23b5c
--- /dev/null
+++ b/bench/build-exists-bro-tree.sml
@@ -0,0 +1,32 @@
+structure BuildExistsBroTree =
+struct
+  fun helpExists (pos, tree, acc) =
+    if pos = Vector.length WordsList.words then
+      acc
+    else
+      let
+        val word = Vector.sub (WordsList.words, pos)
+        val newAcc = BroTree.exists (word, tree)
+        val acc = newAcc orelse acc
+      in
+        helpExists (pos + 1, tree, acc)
+      end
+
+  fun exists (tree) = helpExists (0, tree, true)
+
+  fun main () =
+    let
+      val endTree = Vector.foldl BroTree.insert BroTree.empty WordsList.words
+
+      val startTime = Time.now ()
+      val wordsExist = exists endTree
+      val finishTime = Time.now ()
+
+      val searchDuration = Time.- (finishTime, startTime)
+      val searchDuration = Time.toString searchDuration ^ "\n"
+    in
+      print searchDuration
+    end
+end
+
+val _ = BuildExistsBroTree.main ()
diff --git a/bench/build-exists-string-set b/bench/build-exists-string-set
new file mode 100755
index 0000000..c8534e5
Binary files /dev/null and b/bench/build-exists-string-set differ
diff --git a/bench/build-exists-string-set.mlb b/bench/build-exists-string-set.mlb
new file mode 100644
index 0000000..af629f3
--- /dev/null
+++ b/bench/build-exists-string-set.mlb
@@ -0,0 +1,10 @@
+$(SML_LIB)/basis/basis.mlb
+
+ann
+  "allowVectorExps true"
+in
+  words.sml
+end
+
+../src/string-set.sml
+build-exists-string-set.sml
diff --git a/bench/build-exists-string-set.sml b/bench/build-exists-string-set.sml
new file mode 100644
index 0000000..aab17e8
--- /dev/null
+++ b/bench/build-exists-string-set.sml
@@ -0,0 +1,33 @@
+structure BuildExistsStringSet =
+struct
+  fun helpExists (pos, trie, acc) =
+    if pos = Vector.length WordsList.words then
+      acc
+    else
+      let
+        val word = Vector.sub (WordsList.words, pos)
+        val newAcc = StringSet.exists (word, trie)
+        val acc = newAcc orelse acc
+      in
+        helpExists (pos + 1, trie, acc)
+      end
+
+  fun exists trie = helpExists (0, trie, true)
+
+  fun main () =
+    let
+      val endTrie =
+        Vector.foldl StringSet.insert StringSet.empty WordsList.words
+
+      val startTime = Time.now ()
+      val wordsExist = exists endTrie
+      val finishTime = Time.now ()
+
+      val searchDuration = Time.- (finishTime, startTime)
+      val searchDuration = Time.toString searchDuration ^ "\n"
+    in
+      print searchDuration
+    end
+end
+
+val _ = BuildExistsStringSet.main ()