From 98d669cf07157e275fa796fdd5ad35f3388b0ad1 Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adamc@hcoop.net>
Date: Thu, 6 Nov 2008 17:09:53 -0500
Subject: About to begin optimization of recursive transaction functions

---
 demo/treeFun.ur | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 demo/treeFun.ur

(limited to 'demo/treeFun.ur')

diff --git a/demo/treeFun.ur b/demo/treeFun.ur
new file mode 100644
index 00000000..60633695
--- /dev/null
+++ b/demo/treeFun.ur
@@ -0,0 +1,35 @@
+functor Make(M : sig
+                 type key
+                 con id :: Name
+                 con parent :: Name
+                 con cols :: {Type}
+                 constraint [id] ~ [parent]
+                 constraint [id, parent] ~ cols
+
+                 val key_inj : sql_injectable key
+                 val option_key_inj : sql_injectable (option key)
+
+                 table tab : [id = key, parent = option key] ++ cols
+             end) = struct
+
+    open M
+
+    fun tree (f : $([id = key, parent = option key] ++ cols) -> xbody)
+             (root : option M.key) =
+        let
+            fun recurse (root : option key) =
+                queryX' (SELECT * FROM tab WHERE tab.{parent} = {root})
+                        (fn r =>
+                            children <- recurse (Some r.Tab.id);
+                            return <xml>
+                              <li> {f r.Tab}</li>
+                              
+                              <ul>
+                                {children}
+                              </ul>
+                            </xml>)
+        in
+            recurse root
+        end
+
+end
-- 
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