It works!

app/Main.hs

@@ -15,4 +15,4 @@ myProgram = do
     call "accumulatorLoadNStore"
 
 main :: IO ()
-main = print $ execState myProgram emptyState
+main = print $ runState myProgram emptyState

src/SixtyFiveOhTwo/Instruction.hs

@@ -19,7 +19,7 @@ makeLenses ''InstructionState
 emptyState :: InstructionState
 emptyState = InstructionState { _functionTable = M.empty, _bytestring = B.empty }
 
-type Instruction = State InstructionState InstructionState
+type Instruction = State InstructionState ()
 
 -- This function converts the instructions into a usable bytestring. It's the meat and bones of this DSL.
 runInstructions :: Instruction -> B.ByteString
@@ -60,21 +60,15 @@ appendBytesThenWord bytes word insState = over bytestring (\bs -> B.append bs (B
 
 -- This function allows you to define an instruction opcode that takes no argument
 genericNoByteOp :: Word8 -> Instruction
-genericNoByteOp op = do
-    insState <- get
-    return $ appendBytes [op] insState
+genericNoByteOp op = modify $ appendBytes [op]
 
 -- This function allows you to define an instruction opcode that takes a one byte argument
 genericOp :: Word8 -> Word8 -> Instruction
-genericOp op arg = do
-    insState <- get
-    return $ appendBytes [op, arg] insState
+genericOp op arg = modify $ appendBytes [op, arg]
 
 --  This function allows you to define an instruction opcode that takes a two byte argument
 genericTwoByteOp :: Word8 -> Word16 -> Instruction
-genericTwoByteOp op arg = do
-    insState <- get
-    return $ appendBytesThenWord [op] arg insState
+genericTwoByteOp op arg = modify $ appendBytesThenWord [op] arg
 
 -- This allows you to define subroutines which can be called later using `call`.
 -- Note: your function must end with an `rts`, I don't add that automatically
@@ -83,7 +77,7 @@ define name definition = do
     insState <- get
     let insState' = over functionTable (\fT -> M.insert name (B.length $ insState ^. bytestring) fT) insState
     -- TODO: COMBINE THE FUNCTION DEFINITIONS HERE TOO NOT JUST BYTESTRINGS
-    return $ execState definition insState'
+    put $ execState definition insState'
 
 -- This can be used to call subroutines which were previously `define`d.
 call :: String -> Instruction
@@ -92,7 +86,7 @@ call name = do
     let pointer = case (M.lookup name (insState ^. functionTable)) of
                     Just ptr -> ptr
                     Nothing -> error ("Couldn't find function " ++ name ++ ". Perhaps it wasn't `define`d?")
-    jsr (Absolute $ fromIntegral pointer)
+    put $ execState (jsr (Absolute $ fromIntegral pointer)) insState
 
 -- THE FOLLOWING WAS GENERATED BY
 -- https://github.com/aearnus/assemblicom