diff --git a/src/Interpreter.hs b/src/Interpreter.hs
index 1b897f4..062e58d 100644
--- a/src/Interpreter.hs
+++ b/src/Interpreter.hs
@@ -52,8 +52,8 @@ errorDesc :: Error -> String
 errorDesc NegTape = "ERROR: '<' not working. Cannot access negative tape positions."
 errorDesc LoopNoMatch = "ERROR: '[' or ']' not working. Matching parenthesis not found."
 
-incrInt :: ProgState -> ProgState
-incrInt p = p { ip = ip p + 1 }
+incrIP :: ProgState -> ProgState
+incrIP p = p { ip = ip p + 1 }
 
 execAdd :: ProgState -> Either Error ProgState
 execAdd p = Right p { tape = newTape }
@@ -91,12 +91,19 @@ findMatching prg start wd = case wd of
                 | otherwise          = fmHelper (upd s) acc b ob upd limit
                 where c = prg !! start
 
-execLoopStart :: ProgState -> Either Error ProgState
-execLoopStart w = case newInt of
+execLoop :: WalkingDirection -> ProgState -> Either Error ProgState
+execLoop d w = case posOrF of
             Just n -> Right w { ip = n }
             Nothing -> Left LoopNoMatch
     where jump = (tape w !! dp w) == Byte 0
-          posOrF = if jump then findMatching (program w) (ip w) Forward else Just $ ip w
-          newInt = fmap (+1) posOrF
-
+          posOrF = if jump then findMatching (program w) (ip w) d else Just $ ip w
 
+executeInstruction :: Instruction -> ProgState -> Either Error ProgState
+executeInstruction i = (fmap incrIP) . case i of
+    TapeLeft -> execTapeLeft
+    TapeRight -> execTapeRight
+    Add -> execAdd
+    Sub -> execSub
+    Out -> execOut
+    LoopStart -> execLoop Forward
+    LoopEnd -> execLoop Backward