onError

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/js/urweb.js b/lib/js/urweb.js
index 5ff5b9fb..5cf159ad 100644
--- a/lib/js/urweb.js
+++ b/lib/js/urweb.js
@@ -250,6 +250,18 @@ function pf() {
   whine("Pattern match failure");
 }
 
+var errorHandlers = null;
+
+function onError(f) {
+  errorHandlers = cons(f, errorHandlers);
+}
+
+function er(s) {
+  for (var ls = errorHandlers; ls; ls = ls.next)
+    ls.data(s)(null);
+  throw s;
+}
+
 
 // Remote calls