Added more bindings and error tracebacks.

helper.lua

@@ -8,6 +8,13 @@ end
 function log(...)
   old_print(...)
 end
+function map(tab,func)
+  local new = {}
+  for index,item in pairs(tab) do
+    new[index] = func(item)
+  end
+  return new
+end
 -- HELPER FUNCTIONS
 -- Insert every item in t1 into t0
 function just(...)
@@ -105,7 +112,8 @@ end
 -- Runs a function 
 function assert_meta(...)
   local metas = {...}
-  return function(x,raise)
+  return function(x,raise,handler)
+    handler = handler or error
     local meta = getmetatable(x)
     for tab in iterate(metas) do
       if meta == tab then return end
@@ -124,7 +132,7 @@ function assert_meta(...)
       level = 3
       msg = string.format(raise,msg)
     end
-    error(msg,level)
+    handler(msg,level)
   end
 end