--- a/json.ur	Thu Dec 02 11:35:01 2010 -0500
+++ b/json.ur	Thu Dec 02 11:59:55 2010 -0500
@@ -198,4 +198,57 @@
                                                                        "" => ""
                                                                      | _ => "," ^ acc))
                              "" fl jss names r ^ "}",
-     FromJson = fn _ => error <xml>Uhoh!</xml>}
+     FromJson = fn s =>
+                   let
+                       fun fromJ s (r : $(map option ts)) : $(map option ts) * string =
+                           if String.length s = 0 then
+                               error <xml>JSON object doesn't end in brace</xml>
+                           else if String.sub s 0 = #"}" then
+                               (r, String.substring s {Start = 1, Len = String.length s - 1})
+                           else let
+                                   val (name, s') = unescape s
+                                   val s' = skipSpaces s'
+                                   val s' = if String.length s' = 0 || String.sub s' 0 <> #":" then
+                                                error <xml>No colon after JSON object field naem</xml>
+                                            else
+                                                skipSpaces (String.substring s' {Start = 1, Len = String.length s' - 1})
+
+                                   val (r, s') = @foldR2 [json] [fn _ => string] [fn ts => $(map option ts) -> $(map option ts) * string]
+                                                  (fn [nm ::_] [t ::_] [r ::_] [[nm] ~ r] (j : json t) name' acc r =>
+                                                      if name = name' then
+                                                          let
+                                                              val (v, s') = j.FromJson s'
+                                                          in
+                                                              (r -- nm ++ {nm = Some v}, s')
+                                                          end
+                                                      else
+                                                          let
+                                                              val (r', s') = acc (r -- nm)
+                                                          in
+                                                              (r' ++ {nm = r.nm}, s')
+                                                          end)
+                                                  (fn _ => error <xml>Unknown JSON object field name {[name]}</xml>)
+                                                  fl jss names r
+
+                                   val s' = skipSpaces s'
+                                   val s' = if String.length s' <> 0 && String.sub s' 0 = #"," then
+                                                skipSpaces (String.substring s' {Start = 1, Len = String.length s' - 1})
+                                            else
+                                                s'
+                               in
+                                   fromJ s' r
+                               end
+                   in
+                       if String.length s = 0 || String.sub s 0 <> #"{" then
+                           error <xml>JSON record doesn't begin with brace</xml>
+                       else
+                           let
+                               val (r, s') = fromJ (String.substring s {Start = 1, Len = String.length s - 1})
+                                                   (@map0 [option] (fn [t ::_] => None) fl)
+                           in
+                               (@map2 [option] [fn _ => string] [id] (fn [t] (v : option t) name =>
+                                                                         case v of
+                                                                             None => error <xml>Missing JSON object field {[name]}</xml>
+                                                                           | Some v => v) fl r names, s')
+                           end
+                   end}