diff --git a/README.md b/README.md
index 62bcd62..1b2b8dc 100644
--- a/README.md
+++ b/README.md
@@ -48,4 +48,21 @@ $ rtlil-parse test/corpus/xprop_dffe_1nnd_wrapped_xprop.il -o parsed1.ast
 ```
 
 # TODO
- - [ ] automated CICD on gitea on personal servers
\ No newline at end of file
+ - [ ] automated CICD on gitea on personal servers
+ - [ ] update to have support for four state logic by converting 'X' and 'Z' to zero
+
+# Limitations
+ - Does not support propagating non-two state logic, that is, no
+   support for X or Z values. Default behavior is to reject such
+   input although future iterations may support initializing X and
+   Z to 0.
+ - All cycles in circuit graphs must have at one D Flip-Flop on the
+   cycle path. This requirement necesarily pre-cludes simulation of
+   circuits such as NAND level-resolution SRAMs. The main reason for
+   this restriction is to avoid having to handle metastability in 
+   simulation.
+
+   I have yet to evaluate the implications of how this affects
+   multi-clock domain circuits and their associated primitives such
+   as asynchronous FIFOs, but I plan to make sure simulation of such
+   circuits is possible and correct.
\ No newline at end of file
diff --git a/app/Main.hs b/app/Main.hs
index 8553897..0f7ddaa 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -4,7 +4,7 @@ import System.Environment (getArgs)
 import System.IO
 import Control.Exception (catch, IOException)
 
-import qualified Haskellator
+import Haskellator
 
 main :: IO ()
 main = do
@@ -19,6 +19,7 @@ main = do
             putStrLn "File Contents:"
             putStrLn contents
         [] -> putStrLn "cabal run Haskellator -- <file-path>"
+    putStrLn $ show Haskellator.val
 
 -- Handle potential file reading errors
 handleReadError :: IOException -> IO String
diff --git a/haskellator.cabal b/haskellator.cabal
index 7bfee47..1cad66d 100644
--- a/haskellator.cabal
+++ b/haskellator.cabal
@@ -55,7 +55,9 @@ common warnings
     ghc-options: -Wall
 
 library
-  exposed-modules:     Haskellator
+  exposed-modules:
+    Haskellator,
+    RtlilAstTypes
   other-modules:       
   hs-source-dirs:      src
   build-depends:       
diff --git a/src/Haskellator.hs b/src/Haskellator.hs
index b2cac52..e280220 100644
--- a/src/Haskellator.hs
+++ b/src/Haskellator.hs
@@ -1,33 +1,70 @@
 -- this parser largely references:
 -- https://github.com/YosysHQ/yosys/blob/111b747d2797238eadf541879848492a9d34909a/docs/source/yosys_internals/formats/rtlil_text.rst
-module Haskellator(a) where
+module Haskellator(a, val) where
 
+import Data.Char (digitToInt)
+import Data.List (foldl')
+
+import Control.Monad (void)
 import Text.Parsec
 import Text.Parsec.String (Parser)
+import RtlilAstTypes(
+    PublicId(..), 
+    AutogenId(..),
+    AutoIdxStmt(..),
+    Value(..)
+    )
+
+binaryStringToInt :: String -> Int
+binaryStringToInt = foldl' (\acc x -> acc * 2 + digitToInt x) 0
 
 -- https://github.com/YosysHQ/yosys/blob/111b747d2797238eadf541879848492a9d34909a/frontends/rtlil/rtlil_lexer.l#L88C1-L88C17
 nonws :: Parser Char
 nonws = noneOf " \t\r\n"
 
-pPublicId :: Parser String
-pPublicId = char '\\' *> many1 nonws
+pWs :: Parser String
+pWs = many1 (oneOf " \t")
 
-pAutogenId :: Parser String
-pAutogenId = char '$' *> many1 nonws
+pEol :: Parser String
+pEol = many1 (oneOf "\r\n")
+
+pPublicId   :: Parser PublicId
+pPublicId   = PublicId <$> (char '\\' *> many1 nonws)
+
+pAutogenId  :: Parser AutogenId
+pAutogenId  = AutogenId <$> (char '$' *> many1 nonws)
 
 decimalDigit :: Parser Char
 decimalDigit = oneOf "0123456789"
 
+-- update in the future to support 4 state logic
+-- by converting x and z to 0 and warning about it.
 binaryDigit :: Parser Char
-binaryDigit = oneOf "01xzm-"
+binaryDigit = oneOf "01"
+
+pValue :: Parser Value
+pValue = Value  <$> pInteger 
+                <*> (binaryStringToInt <$> many1 binaryDigit)
 
--- an integer can be positive or negative
 pInteger :: Parser Int
-pInteger = read <$> (pNegInt <|> pPosInt)
-    where
-        pIntAtom = many1 decimalDigit
-        pNegInt = char '-' *> pIntAtom
-        pPosInt = pIntAtom
+pInteger = do
+    sign <- optionMaybe (char '-')
+    digits <- many1 digit
+    let value = read digits
+    return $ case sign of
+        Just _  -> -value
+        Nothing ->  value
+
+pAutogenIdx :: Parser AutoIdxStmt
+pAutogenIdx = AutoIdxStmt <$> (string "autoidx" *> pWs *> pInteger <* pEol)
+
+pModuleEndStmt :: Parser ()
+pModuleEndStmt = void (string "end")
+
+-- pModuleEndStmt :: Parser String
+-- pModuleEndStmt = string "end" <* pEol
+
+val = parse pInteger "pInteger" "721"
 
 a :: Int
 a = 3
\ No newline at end of file
diff --git a/src/RtlilAstTypes.hs b/src/RtlilAstTypes.hs
new file mode 100644
index 0000000..d8e39c1
--- /dev/null
+++ b/src/RtlilAstTypes.hs
@@ -0,0 +1,19 @@
+module RtlilAstTypes(
+    PublicId(..),
+    AutogenId(..),
+    AutoIdxStmt(..),
+    Value(..)
+    ) where
+
+data PublicId       = PublicId      String  deriving (Show)
+data AutogenId      = AutogenId     String  deriving (Show)
+data AutoIdxStmt    = AutoIdxStmt   Int     deriving (Show)
+data Value = Value
+    { width :: Int
+    , value :: Int
+    }
+    deriving (Show)
+data Constant = ConstantValue   Value
+              | ConstantInteger Int
+              | ConstantString  String
+              deriving (Show)