revised callback system to use multiple arguments; added tobitstring function in utility

sim/utility.lua

@@ -51,3 +51,17 @@ function collapseescape(str)
 	
 	return table.concat(ostrt)
 end
+
+function tobitstring(num, len)
+	local maxval = bit.lshift(1, len)
+	if num>=maxval then error("bitstring value too big") end
+	
+	num = num%maxval
+	
+	local bitstring = ""
+	for i = len, 1, -1 do
+		bitstring = bitstring..bit.rshift(bit.band(num, bit.lshift(1, i-1)), i-1)
+	end
+	
+	return bitstring
+end