Proper lifting of MonoEnv stored expressions; avoidance of onchange clobbering

3 files changed, 22 insertions, 1 deletions

diff --git a/lib/js/urweb.js b/lib/js/urweb.js
index 2943c897..d0322bff 100644
--- a/lib/js/urweb.js
+++ b/lib/js/urweb.js
@@ -301,11 +301,19 @@ function inp(t, s, content) {
   return x;
 }
 
+function addOnChange(x, f) {
+  var old = x.onchange;
+  x.onchange = function() { old(); f (); };
+}
+
 
 // Basic string operations
 
 function eh(x) {
-  return x.split("&").join("&amp;").split("<").join("&lt;").split(">").join("&gt;");
+  if (x == null)
+    return "NULL";
+  else
+    return x.split("&").join("&amp;").split("<").join("&lt;").split(">").join("&gt;");
 }
 
 function ts(x) { return x.toString() }
diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index ecec2bec..2ee60538 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -39,3 +39,13 @@ fun mapX (a ::: Type) (ctx ::: {Unit}) f =
     in
         mapX'
     end
+
+fun mapM (m ::: (Type -> Type)) (_ : monad m) (a ::: Type) (b ::: Type) f =
+    let
+        fun mapM' acc ls =
+            case ls of
+                [] => acc
+              | x :: ls => mapM' (x' <- f x; ls' <- acc; return (x' :: ls')) ls
+    in
+        mapM' (return [])
+    end
diff --git a/lib/ur/list.urs b/lib/ur/list.urs
index e9e097d4..d27ad997 100644
--- a/lib/ur/list.urs
+++ b/lib/ur/list.urs
@@ -7,3 +7,6 @@ val rev : a ::: Type -> t a -> t a
 val mp : a ::: Type -> b ::: Type -> (a -> b) -> t a -> t b
 
 val mapX : a ::: Type -> ctx ::: {Unit} -> (a -> xml ctx [] []) -> t a -> xml ctx [] []
+
+val mapM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type
+           -> (a -> m b) -> list a -> m (list b)