From 22c9a2d5a054bd3e0b74ac46a13e67cada2fe450 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Wed, 1 Jul 2015 14:27:16 -0400
Subject: [PATCH] tt_dict_singleton

---
 critbit.c | 9 ++++++++-
 critbit.h | 6 ++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/critbit.c b/critbit.c
index 09cde62..35523f2 100644
--- a/critbit.c
+++ b/critbit.c
@@ -125,13 +125,20 @@ static int set_walk(tt_arena_t *a,
   }
 }
 
+tt_node_ptr_t tt_dict_singleton(tt_arena_t *a,
+				tt_atom_t key,
+				tt_node_ptr_t trie)
+{
+  return tt_cons_dict(a, RET_IF_NO_PTR(tt_cons_leaf(a, trie, key)), 1);
+}
+
 tt_node_ptr_t tt_dict_set(tt_arena_t *a,
 			  tt_node_ptr_t t,
 			  tt_atom_t key,
 			  tt_node_ptr_t trie)
 {
   if (TT_EMPTY_DICT_P(t)) {
-    return tt_cons_dict(a, RET_IF_NO_PTR(tt_cons_leaf(a, trie, key)), 1);
+    return tt_dict_singleton(a, key, trie);
   }
 
   assert(tt_ptr_tag(t) == TT_TAG_DICT);
diff --git a/critbit.h b/critbit.h
index 2800941..9a72921 100644
--- a/critbit.h
+++ b/critbit.h
@@ -10,6 +10,12 @@ extern int tt_dict_size(tt_arena_t *a, tt_node_ptr_t t);
 /* Returns TT_NO_PTR when key not present. Does not manipulate references. */
 extern tt_node_ptr_t tt_dict_get(tt_arena_t *a, tt_node_ptr_t t, tt_atom_t key);
 
+/* Returns TT_NO_PTR when allocation failed. Otherwise, a length-one dict.
+   Grabs `trie` if required. */
+extern tt_node_ptr_t tt_dict_singleton(tt_arena_t *a,
+				       tt_atom_t key,
+				       tt_node_ptr_t trie);
+
 /* Returns TT_NO_PTR when allocation failed. Otherwise, yields a dict.
    Grabs `trie` if required. */
 extern tt_node_ptr_t tt_dict_set(tt_arena_t *a,