1 files changed, 13 insertions, 3 deletions

diff --git a/src/Lib.hs b/src/Lib.hs
index 4f4d2f3..5d58008 100644
--- a/src/Lib.hs
+++ b/src/Lib.hs
@@ -5,6 +5,7 @@ module Lib
   ) where
 
 import           Term
+import           Utils
 
 data State = L | R
 
@@ -17,13 +18,22 @@ k = Abs (Abs (Idx 1))
 i :: Term
 i = Abs (Idx 0)
 
+clean :: String -> String
+clean (x : xs) | x == '0' || x == '1' = x : clean xs
+               | otherwise            = clean xs
+clean [] = []
+
 -- reverse wouldn't be needed if [0F] instead of [F0]
-fromJotter :: String -> Term
-fromJotter = go L . reverse
+fromCleanJotter :: String -> Term
+fromCleanJotter t | even $ length t = go L $ reverse t
+                  | otherwise       = go R $ reverse t
  where
   go L ('0' : xs) = App s (go R xs)
   go R ('0' : xs) = App (go L xs) s
   go L ('1' : xs) = App k (go R xs)
   go R ('1' : xs) = App (go L xs) k
-  go d (_   : xs) = go d xs
   go _ []         = i
+  go _ _          = invalid
+
+fromJotter :: String -> Term
+fromJotter = fromCleanJotter . clean