1 files changed, 13 insertions, 3 deletions

diff --git a/lib/js/urweb.js b/lib/js/urweb.js
index 653f8d2f..6ca4becd 100644
--- a/lib/js/urweb.js
+++ b/lib/js/urweb.js
@@ -632,7 +632,7 @@ function rc(prefix, uri, parse, k, needsSig) {
 
       if (isok) {
         try {
-          execF(k, parse(xhr.responseText));
+          k(parse(xhr.responseText));
         } catch (v) {
           doExn(v);
         }
@@ -854,7 +854,11 @@ function execP(env, p, v) {
 }
 
 function exec0(env, e) {
-  var stack = null;
+  return exec1(env, null, e);
+}
+
+function exec1(env, stack, e) {
+  var stack, usedK = false;
 
   var saveEnv = function() {
     if (stack.next != null && stack.next.data.c != "<")
@@ -883,8 +887,9 @@ function exec0(env, e) {
       case "f":
         fr.args[fr.pos++] = v;
         if (fr.a == null) {
-          e = {c: "c", v: fr.f.apply(null, fr.args)};
           stack = stack.next;
+          e = {c: "c", v: fr.f.apply(null, fr.args)};
+          if (usedK) return null;
         } else {
           e = fr.a.data;
           fr.a = fr.a.next;
@@ -1014,6 +1019,11 @@ function exec0(env, e) {
       env = e.env;
       e = e.body;
       break;
+    case "K":
+      { var savedStack = stack.next, savedEnv = env;
+      e = {c: "c", v: function(v) { return exec1(savedEnv, savedStack, {c: "c", v: v}); } };}
+      usedK = true;
+      break;      
     default:
       whine("Unknown Ur expression kind " + e.c);
     }