# HG changeset patch
# User Adam Chlipala <adam@chlipala.net>
# Date 1290372204 18000
# Node ID 80bff6449f4162fb16a7c1f9035f6a0d3ad8ec0f
# Parent  4172863d049df21725cf8619703cde41b20a8dc6
Fix a bug in C list unurlification

diff -r 4172863d049d -r 80bff6449f41 lib/ur/list.ur
--- a/lib/ur/list.ur	Sat Nov 20 10:45:22 2010 -0500
+++ b/lib/ur/list.ur	Sun Nov 21 15:43:24 2010 -0500
@@ -308,6 +308,20 @@
         sort' ls
     end
 
+val nth [a] =
+    let
+        fun nth (ls : list a) (n : int) : option a =
+            case ls of
+                [] => None
+              | x :: ls' =>
+                if n <= 0 then
+                    Some x
+                else
+                    nth ls' (n-1)
+    in
+        nth
+    end
+
 fun assoc [a] [b] (_ : eq a) (x : a) =
     let
         fun assoc' (ls : list (a * b)) =
diff -r 4172863d049d -r 80bff6449f41 lib/ur/list.urs
--- a/lib/ur/list.urs	Sat Nov 20 10:45:22 2010 -0500
+++ b/lib/ur/list.urs	Sun Nov 21 15:43:24 2010 -0500
@@ -71,6 +71,8 @@
 
 val sort : a ::: Type -> (a -> a -> bool) (* > predicate *) -> t a -> t a
 
+val nth : a ::: Type -> list a -> int -> option a
+
 (** Association lists *)
 
 val assoc : a ::: Type -> b ::: Type -> eq a -> a -> t (a * b) -> option b
diff -r 4172863d049d -r 80bff6449f41 src/cjr_print.sml
--- a/src/cjr_print.sml	Sat Nov 20 10:45:22 2010 -0500
+++ b/src/cjr_print.sml	Sun Nov 21 15:43:24 2010 -0500
@@ -861,7 +861,7 @@
                                   space,
                                   string "+=",
                                   space,
-                                  string "3, NULL) : ((!strncmp(request, \"Cons\", 4) && (request[4] == 0 ",
+                                  string "3, (*request == '/' ? *request++ = 0 : 0), NULL) : ((!strncmp(request, \"Cons\", 4) && (request[4] == 0 ",
                                   string "|| request[4] == '/')) ? (request",
                                   space,
                                   string "+=",
@@ -895,7 +895,7 @@
                                   newline,
                                   string ":",
                                   space,
-                                  string ("(uw_error(ctx, FATAL, \"Error unurlifying list\"), NULL))));"),
+                                  string ("(uw_error(ctx, FATAL, \"Error unurlifying list: %s\", request), NULL))));"),
                                   newline],
                              string "}",
                              newline,