--- a/core/src/luan/modules/Io.luan	Thu Aug 27 08:35:03 2015 -0600
+++ b/core/src/luan/modules/Io.luan	Sun Aug 30 11:37:39 2015 -0600
@@ -72,10 +72,11 @@
 
 -- repr
 
-local function do_repr(obj,done)
+local function do_repr(obj,strict,done)
 	local tp = type(obj)
 	if tp == "table" then
 		if done[obj] == true then
+			strict and error "circular reference"
 			%><circular reference><%
 			return
 		end
@@ -85,7 +86,7 @@
 		local in_list = {}
 		for key, value in ipairs(obj) do
 			if is_first then is_first = false else %>, <% end
-			do_repr(value,done)
+			do_repr(value,strict,done)
 			in_list[key] = true
 		end
 		for key, value in pairs(obj) do
@@ -96,9 +97,9 @@
 				elseif type(key) == "table" then
 					%>[<<%=key%>>]<%
 				else
-					%>[<%do_repr(key,done)%>]<%
+					%>[<%do_repr(key,strict,done)%>]<%
 				end
-				%>=<% do_repr(value,done)
+				%>=<% do_repr(value,strict,done)
 			end
 		end
 		%>}<%
@@ -107,12 +108,13 @@
 	elseif tp == "nil" or tp == "boolean" or tp == "number" then
 		%><%=obj%><%
 	else
+		strict and error("can't repr type '"..tp.."' of "..obj)
 		%><<%=obj%>><%
 	end
 end
 
-function M.repr(obj)
-	return M.output_of(do_repr,obj,{})
+function M.repr(obj,strict)
+	return M.output_of(do_repr,obj,strict or false,{})
 end