diff --git a/CG.hs b/CG.hs
new file mode 100644
--- /dev/null
+++ b/CG.hs
@@ -0,0 +1,395 @@
+{-# LANGUAGE OverloadedStrings, ViewPatterns, FlexibleContexts, PartialTypeSignatures, TupleSections, RecordWildCards, ScopedTypeVariables #-}
+module Main where
+
+
+import           Prelude hiding (lex)
+import           Control.Exception (IOException, handle)
+import           Control.Monad (forM,forM_,when,unless)
+import           Data.List (stripPrefix)
+import           Data.List.Split (splitOn)
+import           Data.Map (Map)
+import           Data.Maybe (fromMaybe,maybe)
+import qualified Data.Text as T
+import qualified Data.Text.IO as T
+import           Data.Void (Void)
+import           System.Console.GetOpt (OptDescr(..),ArgDescr(..),ArgOrder(..),usageInfo,getOpt)
+import           System.Directory (renameFile,doesFileExist,getDirectoryContents,createDirectoryIfMissing)
+import           System.Environment (getProgName,getArgs,getEnv)
+import           System.Exit (ExitCode(..), exitSuccess, exitFailure)
+import           System.FilePath (takeBaseName,dropExtension,(</>),(<.>),(-<.>))
+import           System.IO
+import           System.Process
+import qualified Text.Parsec as P (parse)
+import           Text.Printf (printf)
+
+import           CG.Prover
+import           CG.Parser
+import           CG.Base hiding (Term)
+import           CG.Parsing
+import           CG.ToAgda
+
+
+descInstalled :: FilePath -> IO ()
+descInstalled dir = do
+  let
+    readDesc :: FilePath -> IO (Maybe String)
+    readDesc f =
+      handle (\(e :: IOException) -> return Nothing)
+      (stripPrefix "-- " . T.unpack <$> withFile f ReadMode T.hGetLine)
+
+  filesAndDirectories <- getDirectoryContents dir
+  forM_ filesAndDirectories $ \fileOrDirectory -> do
+    isFile <- doesFileExist (dir </> fileOrDirectory)
+    when isFile $ do
+      mbDesc <- readDesc (dir </> fileOrDirectory)
+      case mbDesc of
+       Nothing   -> return ()
+       Just desc -> do
+         putStrLn (printf "%s%-32s  %s" (replicate 19 ' ') fileOrDirectory desc)
+
+
+
+main :: IO ()
+main = do
+
+  args <- getArgs
+
+  let (actions, _, _) = getOpt Permute options args
+  opts <- foldl (>>=) (return defaultOptions) actions
+  let Options { optTasks   = tasks
+              , optLexicon = mbLexicon
+              , optSystem  = sys@System{..}
+              , optOutput  = out
+              , optGoal    = g
+              , optDepth   = d
+              , optVerbose = verbose
+              } = opts
+
+  let
+    mbHandles :: IO (Maybe Handle, Maybe Handle)
+    mbHandles =
+      if verbose then return (Nothing, Nothing)
+      else do f <- openFile "/dev/null" AppendMode; return (Just f, Just f)
+
+    -- run a command
+    runCommand :: String -> [String] -> Maybe FilePath -> IO ()
+    runCommand cmd args dir = do
+      putStrLn (showCommandForUser cmd args)
+      (mbOut,mbErr) <- mbHandles
+      p <- runProcess cmd args dir Nothing Nothing mbOut mbErr
+      e <- waitForProcess p
+      case e of
+       ExitSuccess   -> return ()
+       ExitFailure r -> error ("Error in `"++cmd++"' (exit "++show r++")")
+
+    -- use the given lexicon, otherwise read the default lexicon
+    givenOrDefaultLexicon :: IO (Map String (Term ConId Void))
+    givenOrDefaultLexicon = case mbLexicon of
+      Just lx -> return lx
+      Nothing -> do hPutStrLn stderr "Reading default lexicon..."; readLexicon "default"
+
+
+  when (null tasks)
+       (putStrLn "Usage: For basic information, try the `--help' option.")
+
+  let
+    runTask :: Task -> IO [Result]
+    runTask (Solve str) = case P.parse judgement "" str of
+      Left  e -> error (show e)
+      Right g -> return $ map (uncurry Solved) (solve sys d [g])
+    runTask (Parse sent expr) = do
+      lx <- givenOrDefaultLexicon
+      return (map (uncurry $ Parsed sent expr) (parse sys d lx sent g))
+
+  proofs <- concat <$> mapM runTask tasks
+
+  let
+    generateAgda :: Maybe FilePath -> IO [FilePath]
+    generateAgda  Nothing  = writeAgdaFile stdout "Main" sys proofs g
+    generateAgda (Just fn) = withFile fn WriteMode (\h -> writeAgdaFile h (takeBaseName fn) sys proofs g)
+
+    generateLaTeX :: Maybe FilePath -> IO [FilePath]
+    generateLaTeX targetDir = do
+      home <- fromMaybe "." <$> getCgHome
+
+      let mainFile = home </> "Main.agda"
+      createDirectoryIfMissing True home
+      fileList    <- withFile mainFile WriteMode (\h -> writeAgdaFile h "Main" sys proofs g)
+
+      agdaInclude <- map ("-i"++) . (home:) . splitOn ":" <$> getEnv "AGDA_PATH"
+      let args = "--compile" : "--compile-dir" : home : agdaInclude ++ [mainFile]
+
+      runCommand "agda" args (Just home)
+      runCommand (dropExtension mainFile) [] targetDir
+
+      return fileList
+
+    generatePNG :: Maybe FilePath -> IO [FilePath]
+    generatePNG mbDir = do
+
+      let targetDir = fromMaybe "." mbDir
+      home <- fromMaybe "." <$> getCgHome
+      latexFiles <- generateLaTeX (Just home)
+
+      forM_ latexFiles $ \latexFile -> do
+
+        putStrLn ("Processing `"++latexFile++"'...")
+
+        contents <- readFile (home </> latexFile <.> "tex")
+        writeFile (home </> latexFile <.> "standalone_tex") . unlines $
+          [ "\\documentclass[preview,border={10pt 10pt 50pt 10pt}]{standalone}"
+          , preamble
+          , "\\begin{document}"
+          , contents
+          , "\\end{document}"
+          ]
+
+        let args1 = ["-shell-escape"
+                    ,"-output-directory",home
+                    ,latexFile <.> "standalone_tex"]
+        runCommand "pdflatex" args1 (Just home)
+
+        let args2 = ["-density","300"
+                    ,home </> latexFile <.> "pdf"
+                    ,"-quality","90"
+                    ,home </> latexFile <.> "png"]
+        runCommand "convert" args2 (Just home)
+
+        renameFile (home </> latexFile <.> "png") (targetDir </> latexFile <.> "png")
+
+      return latexFiles
+
+  case out of
+    StdOut         -> mapM_ printResult proofs
+    AgdaFile fn -> do maybe (return ()) checkFile fn; generateAgda fn; return ()
+    LaTeX    mb -> do generateLaTeX mb >>= mapM_ (putStrLn . (<.> "tex"))
+    PNG      mb -> do generatePNG mb >>= mapM_ (putStrLn . (<.> "png"))
+
+
+-- * Command-Line Options
+
+data Task
+  = Solve String
+  | Parse String [String]
+
+data Output
+  = StdOut                    -- ^ Print proofs to the standard output.
+  | AgdaFile (Maybe FilePath) -- ^ Convert proofs to an Agda program and print it.
+  | LaTeX    (Maybe FilePath) -- ^ Convert proofs to LaTeX files.
+  | PNG      (Maybe FilePath) -- ^ Convert proofs to PNG files.
+
+data Options = Options
+  { optTasks      :: [Task]
+  , optLexicon    :: Maybe (Map String (Term ConId Void))
+  , optSystem     :: System ConId
+  , optOutput     :: Output
+  , optGoal       :: Term ConId Void
+  , optDepth      :: Int
+  , optVerbose    :: Bool
+  }
+
+defaultOptions :: Options
+defaultOptions    = Options
+  { optTasks      = []
+  , optLexicon    = Nothing
+  , optSystem     = error "System must be specified."
+  , optOutput     = StdOut
+  , optGoal       = Con (NegAtom "s") []
+  , optDepth      = 5
+  , optVerbose    = False
+  }
+
+options :: [ OptDescr (Options -> IO Options) ]
+options =
+  [ Option [] ["solve"]
+    (ReqArg (\arg opt -> return opt { optTasks = optTasks opt ++ [Solve arg] }) "SEQUENT")
+    "Search for proof of a sequent."
+
+  , Option [] ["parse"]
+    (ReqArg (\arg opt -> return opt { optTasks = optTasks opt ++ [Parse arg []] }) "SENTENCE")
+    "Parse the given sentence."
+
+  , Option [] ["to","or"]
+    (ReqArg addExpected "EXPRESSION")
+    "Generate check if the previous test results in this expression."
+
+  , Option "s" ["system"]
+    (ReqArg (\arg opt -> do sys <- readSystem arg; return opt { optSystem = sys }) "SYSTEM_FILE")
+    "Type-logical system (see below)."
+
+  , Option "d" ["depth"]
+    (ReqArg (\arg opt -> return opt { optDepth = read arg }) "SEARCH_DEPTH")
+    "Set the search depth. For systems marked as `infinite' only. Defaults to `5'."
+
+  , Option "l" ["lexicon"]
+    (ReqArg (\arg opt -> do lex <- readLexicon arg; return opt { optLexicon = Just lex }) "LEXICON_FILE")
+    "Lexicon used in parsing. Defaults to `$CGTOOL_HOME/lex/default'."
+
+  , Option "g" ["goal"]
+    (ReqArg (\arg opt -> do g <- parseGoal arg; return opt { optGoal = g }) "GOAL_FORMULA")
+    "Goal formula for parsing. Defaults to `s⁻'."
+
+  , Option [] ["to-agda"]
+    (OptArg (\arg opt -> do return opt { optOutput = AgdaFile arg }) "AGDA_FILE")
+    "Produce an Agda module, and write it to the given file (or stdout)."
+
+  , Option [] ["to-latex"]
+    (OptArg (\arg opt -> do return opt { optOutput = LaTeX arg }) "DIRECTORY")
+    "Produce a TeX file for each proof, and write it to DIRECTORY."
+
+  , Option [] ["to-png"]
+    (OptArg (\arg opt -> do return opt { optOutput = PNG arg }) "DIRECTORY")
+    "Produce a PNG file for each proof, and write it to DIRECTORY."
+
+  , Option "v" ["verbose"]
+    (NoArg (\opt -> return opt { optVerbose = True }))
+    "Verbose output."
+
+  , Option "h" ["help"]
+    (NoArg  (\_ -> do
+              prg <- getProgName
+              hPutStrLn stderr (usageInfo prg options)
+              mbCgHome <- getCgHome
+              case mbCgHome of
+               Nothing     -> do
+                 putStrLn "Warning: `$CGTOOL_HOME' is not set."
+                 exitFailure
+               Just cgHome -> do
+                 hPutStrLn stderr (printf "\nAvailable systems (in `%s')\n" (cgHome </> "sys"))
+                 descInstalled (cgHome </> "sys")
+                 hPutStrLn stderr (printf "\nAvailable lexicons (in `%s')\n" (cgHome </> "lex"))
+                 descInstalled (cgHome </> "lex")
+                 exitSuccess
+            ))
+    "Show help."
+  ]
+
+
+
+-- * Helper functions
+
+compileAgda :: FilePath -> FilePath -> IO ExitCode
+compileAgda dir mainFile = do
+  agdaInclude <- map ("-i"++) . (dir:) . splitOn ":" <$> getEnv "AGDA_PATH"
+  let args = "--compile" : "--compile-dir" : dir : agdaInclude ++ [mainFile]
+  (ext,out,err) <- readProcessWithExitCode "agda" args ""
+  case ext of
+   ExitSuccess -> return ExitSuccess
+   _           -> do hPutStrLn stdout out; hPutStrLn stderr err; return ext
+
+-- |Check if a given file exists, and if so ask for a confirmation
+--  for overwriting the file.
+checkFile :: FilePath -> IO ()
+checkFile fn = do
+  fileExists <- doesFileExist fn
+  unless fileExists $ do
+    hSetBuffering stdout NoBuffering
+    putStr (fn ++ " exists. Overwrite? (y/n) ")
+    hSetBuffering stdin NoBuffering
+    hSetEcho stdin False
+    hFlushInput stdin
+    answer <- yorn
+    when (answer == 'Y') exitSuccess
+  where
+    hFlushInput hdl = do
+      r <- hReady hdl
+      when r (hGetChar hdl >> hFlushInput hdl)
+
+    yorn = do
+      c <- getChar
+      if c == 'Y' || c == 'N' then return c
+      else if c == 'y' then return 'Y'
+      else if c == 'n' then return 'N'
+      else yorn
+
+
+-- |Print results.
+printResult :: Result -> IO ()
+printResult (Solved     g p) = do print g; print p
+printResult (Parsed s _ g p) = do putStrLn s; print g; print p
+
+
+-- |Add an expected result to the most recent @Parse@ task.
+addExpected :: String -> Options -> IO Options
+addExpected expr opt@Options{..} = do
+  progName <- getProgName
+
+  when (null optTasks) $
+    do putStrLn ("Usage: "++progName++"--parse SENTENCE --to "
+                 ++"EXPRESSION [--or EXPRESSION]"); exitFailure
+
+  let lastTask = last optTasks
+
+  unless (isParse lastTask) $
+    do putStrLn ("Usage: "++progName++"--parse SENTENCE --to "
+                 ++"EXPRESSION [--or EXPRESSION]"); exitFailure
+
+  let (Parse sent exprs) = lastTask
+  return opt { optTasks = init optTasks ++ [Parse sent (exprs ++ [expr])]}
+
+
+-- |Check if given Task is a parse-task with no expected result.
+isParse :: Task -> Bool
+isParse (Parse _ _) = True
+isParse _           = False
+
+
+-- preamble.tex
+preamble :: String
+preamble = unlines
+  [ "\\usepackage{adjustbox}%"
+  , "\\usepackage[labelformat=empty]{caption}%"
+  , "\\usepackage{amssymb}%"
+  , "\\usepackage{amsmath}%"
+  , "\\usepackage{bussproofs}%"
+  , "\\usepackage[usenames,dvipsnames]{color}%"
+  , "\\usepackage{etoolbox}%"
+  , "\\usepackage{mdframed}%"
+  , "\\usepackage{pict2e}%"
+  , "\\usepackage{picture}%"
+  , "\\usepackage{scalerel}%"
+  , "\\usepackage{stmaryrd}%"
+  , "\\usepackage{textgreek}%"
+  , "\\usepackage{ucs}%"
+  , "\\usepackage[utf8x]{inputenc}%"
+  , "\\usepackage{xifthen}%"
+  , ""
+  , "\\EnableBpAbbreviations%"
+  , ""
+  , "\\makeatletter"
+  , "\\newcommand{\\pictslash}[2]{%"
+  , "  \\vcenter{%"
+  , "    \\sbox0{$\\m@th#1\\varobslash$}\\dimen0=.55\\wd0"
+  , "    \\hbox to\\wd 0{%"
+  , "      \\hfil\\pictslash@aux#2\\hfil"
+  , "    }%"
+  , "  }%"
+  , "}"
+  , "\\newcommand{\\pictslash@aux}[2]{%"
+  , "    \\begin{picture}(\\dimen0,\\dimen0)"
+  , "    \\roundcap"
+  , "    \\linethickness{.15ex}"
+  , "    \\put(0,#1\\dimen0){\\line(1,#2){\\dimen0}}"
+  , "    \\end{picture}%"
+  , "}"
+  , "\\makeatother"
+  , ""
+  , "\\newcommand{\\varslash}{%"
+  , "  \\mathbin{\\mathpalette\\pictslash{{0}{1}}}%"
+  , "}"
+  , "\\newcommand{\\varbslash}{%"
+  , "  \\mathbin{\\mathpalette\\pictslash{{1}{-1}}}%"
+  , "}"
+  , "\\newcommand{\\focus}[1]{%"
+  , "  \\adjustbox{padding=.4em .15ex .1em .15ex,bgcolor=Cyan}{%"
+  , "    \\ensuremath{\\color{white}\\rule[-4pt]{0pt}{14pt}#1}"
+  , "  }%"
+  , "}"
+  , ""
+  , "\\newcommand{\\varbox}[1][]{\\ifthenelse{\\isempty{#1}}{\\Box}{\\,[\\,#1\\,]\\,}}"
+  , "\\newcommand{\\vardia}[1][]{\\ifthenelse{\\isempty{#1}}{\\Diamond}{\\,\\langle\\,#1\\,\\rangle\\,}}"
+  , "\\newcommand{\\varpref}[1]{{}_{#1}}"
+  , "\\newcommand{\\varsuff}[1]{{}^{#1}}"
+  , "\\newcommand{\\vardown}[1]{\\,\\cdot\\,#1\\,\\cdot\\,}"
+  , "\\renewcommand{\\fCenter}{\\mathbin{\\vdash}}"
+  ]
diff --git a/CG/Base.hs b/CG/Base.hs
new file mode 100644
--- /dev/null
+++ b/CG/Base.hs
@@ -0,0 +1,260 @@
+{-# LANGUAGE DeriveGeneric, TypeSynonymInstances, FlexibleInstances,
+    FlexibleContexts, RecordWildCards, UndecidableInstances #-}
+module CG.Base (ConId(..)
+               ,nullary,unary,binary
+               ,unaryLogical,unaryStructural
+               ,binaryLogical,binaryStructural
+               ,sequents
+               ,toLogical,toStructural
+               ,ASCII(..),Result(..)
+               ,module X
+               ) where
+
+
+import CG.Prover as X
+import Control.DeepSeq (NFData)
+import Data.Hashable   (Hashable)
+import Data.Serialize  (Serialize)
+import Data.Void       (Void)
+import GHC.Generics    (Generic)
+
+
+-- * Operators
+
+data ConId
+
+  -- atomic formulas
+  = PosAtom String
+  | NegAtom String
+
+  -- mediator between logical and structural formulas
+  | Down
+
+  -- logical operators
+  | FProd | FImpR | FImpL
+  | FPlus | FSubL | FSubR
+  | F0L   | F0R   | FBox
+  | F1L   | F1R   | FDia
+
+  -- structural operators
+  | SProd | SImpR | SImpL
+  | SPlus | SSubL | SSubR
+  | S0L   | S0R   | SBox
+  | S1L   | S1R   | SDia
+  | Comma
+
+  -- hollow product and slashes
+  | HProd | HImpR | HImpL
+
+  -- sequents
+  | JAlgebr | JStruct
+  | JFocusL | JFocusR
+
+  deriving (Eq,Ord,Show,Generic)
+
+
+instance Hashable  ConId
+instance NFData    ConId
+instance Serialize ConId
+
+
+-- * Groupings of operators.
+
+unaryLogical :: [ConId]
+unaryLogical = [F0L, F0R, FBox, F1L, F1R, FDia, HProd, HImpR, HImpL]
+
+unaryStructural :: [ConId]
+unaryStructural = [S0L, S0R, SBox, S1L, S1R, SDia]
+
+binaryLogical :: [ConId]
+binaryLogical = [FProd, FImpR, FImpL, FPlus, FSubL, FSubR]
+
+binaryStructural :: [ConId]
+binaryStructural = [SProd, SImpR, SImpL, SPlus, SSubL, SSubR, Comma]
+
+sequents :: [ConId]
+sequents = [JAlgebr, JStruct, JFocusL, JFocusL]
+
+
+-- |Convert structural operators to their logical equivalents.
+toLogical :: ConId -> ConId
+toLogical SProd = FProd
+toLogical SImpR = FImpR
+toLogical SImpL = FImpL
+toLogical SPlus = FPlus
+toLogical SSubL = FSubL
+toLogical SSubR = FSubR
+toLogical S0L   = F0L
+toLogical S0R   = F0R
+toLogical SBox  = FBox
+toLogical S1L   = F1L
+toLogical S1R   = F1R
+toLogical SDia  = FDia
+toLogical c     = c
+
+
+-- |Convert logical operators to their structural equivalents.
+toStructural :: ConId -> ConId
+toStructural FProd = SProd
+toStructural FImpR = SImpR
+toStructural FImpL = SImpL
+toStructural FPlus = SPlus
+toStructural FSubL = SSubL
+toStructural FSubR = SSubR
+toStructural F0L   = S0L
+toStructural F0R   = S0R
+toStructural FBox  = SBox
+toStructural F1L   = S1L
+toStructural F1R   = S1R
+toStructural FDia  = SDia
+toStructural c     = c
+
+
+-- * Utility constructors
+
+nullary :: ConId -> Term ConId v
+nullary c = Con c []
+
+unary   :: ConId -> Term ConId v -> Term ConId v
+unary   c x = Con c [x]
+
+binary  :: ConId -> Term ConId v -> Term ConId v -> Term ConId v
+binary  c x y = Con c [x,y]
+
+
+-- * Guards
+
+instance Guardable ConId where
+
+  isAtomic (Con (PosAtom _) _) = True
+  isAtomic (Con (NegAtom _) _) = True
+  isAtomic _                   = False
+
+  isPositive (Var          _)    = True
+  isPositive (Con (PosAtom _) _) = True
+  isPositive (Con (NegAtom _) _) = False
+  isPositive (Con  FProd   _)    = True
+  isPositive (Con  FSubL   _)    = True
+  isPositive (Con  FSubR   _)    = True
+  isPositive (Con  HProd   _)    = True
+  isPositive (Con  F1L     _)    = True
+  isPositive (Con  F1R     _)    = True
+  isPositive (Con  FDia    _)    = True
+  isPositive _                   = False
+
+  isNegative (Var          _)    = True
+  isNegative (Con (PosAtom _) _) = False
+  isNegative (Con (NegAtom _) _) = True
+  isNegative (Con  FPlus   _)    = True
+  isNegative (Con  FImpR   _)    = True
+  isNegative (Con  FImpL   _)    = True
+  isNegative (Con  HImpR   _)    = True
+  isNegative (Con  HImpL   _)    = True
+  isNegative (Con  F0L     _)    = True
+  isNegative (Con  F0R     _)    = True
+  isNegative (Con  FBox    _)    = True
+  isNegative _                   = False
+
+
+
+-- * Printing
+
+instance ToString ConId where
+  toString (PosAtom x) = x
+  toString (NegAtom x) = x ++ "⁻"
+  toString F0L     = "₀"; toString F0R     = "⁰"; toString FBox  = "□"
+  toString F1L     = "₁"; toString F1R     = "¹"; toString FDia  = "◇"
+  toString FProd   = "⊗"; toString FImpR   = "⇒"; toString FImpL = "⇐"
+  toString SProd   = "⊗"; toString SImpR   = "⇒"; toString SImpL = "⇐"
+  toString HProd   = "∘"; toString HImpR   = "⇨"; toString HImpL = "⇦"
+  toString FPlus   = "⊕"; toString FSubL   = "⇚"; toString FSubR = "⇛"
+  toString SPlus   = "⊕"; toString SSubL   = "⇚"; toString SSubR = "⇛"
+  toString S0L     = "₀"; toString S0R     = "⁰"; toString SBox  = "[]"
+  toString S1L     = "₁"; toString S1R     = "¹"; toString SDia  = "⟨⟩"
+  toString JAlgebr = "⊢"; toString JStruct = "⊢"
+  toString JFocusL = "⊢"; toString JFocusR = "⊢"
+  toString Down    = "·"; toString Comma   = ","
+
+instance Operator ConId where
+
+  prec (PosAtom _) = 0
+  prec (NegAtom _) = 0
+  prec F0L     = 9; prec F0R     = 9; prec FBox  = 9
+  prec F1L     = 9; prec F1R     = 9; prec FDia  = 9
+  prec FProd   = 8; prec FImpR   = 7; prec FImpL = 7
+  prec FPlus   = 8; prec FSubL   = 7; prec FSubR = 7
+  prec HProd   = 8; prec HImpR   = 7; prec HImpL = 7
+  prec S0L     = 6; prec S0R     = 6; prec SBox  = 0
+  prec S1L     = 6; prec S1R     = 6; prec SDia  = 0
+  prec SProd   = 5; prec SImpR   = 4; prec SImpL = 4
+  prec SPlus   = 5; prec SSubL   = 4; prec SSubR = 4
+  prec JAlgebr = 0; prec JStruct = 0
+  prec JFocusL = 0; prec JFocusR = 0
+  prec Down    = 0; prec Comma   = 3
+
+  template (PosAtom x) _ = showString x . showChar ' '
+  template (NegAtom x) _ = showString x . showString "⁻ "
+  template F0L     [x]   = showString "₀ " . x
+  template F0R     [x]   = x . showString "⁰ "
+  template FBox    [x]   = showString "□ " . x
+  template F1L     [x]   = showString "₁ " . x
+  template F1R     [x]   = x . showString "¹ "
+  template FDia    [x]   = showString "◇ " . x
+  template FProd   [x,y] = x . showString "⊗ " . y
+  template FImpR   [x,y] = x . showString "⇒ " . y
+  template FImpL   [x,y] = x . showString "⇐ " . y
+  template SProd   [x,y] = x . showString "⊗ " . y
+  template SImpR   [x,y] = x . showString "⇒ " . y
+  template SImpL   [x,y] = x . showString "⇐ " . y
+  template HProd   [x,y] = x . showString "∘ " . y
+  template HImpR   [x,y] = x . showString "⇨ " . y
+  template HImpL   [x,y] = x . showString "⇦ " . y
+  template FPlus   [x,y] = x . showString "⊕ " . y
+  template FSubL   [x,y] = x . showString "⇚ " . y
+  template FSubR   [x,y] = x . showString "⇛ " . y
+  template SPlus   [x,y] = x . showString "⊕ " . y
+  template SSubL   [x,y] = x . showString "⇚ " . y
+  template SSubR   [x,y] = x . showString "⇛ " . y
+  template S0L     [x]   = showString "₀ " . x
+  template S0R     [x]   = x . showString "⁰ "
+  template SBox    [x]   = showString "[ " . x . showString "]"
+  template S1L     [x]   = showString "₁ " . x
+  template S1R     [x]   = x . showString "¹ "
+  template SDia    [x]   = showString "⟨ " . x . showString "⟩"
+  template JAlgebr [x,y] = x . showString "⊢ " . y
+  template JStruct [x,y] = x . showString "⊢ " . y
+  template JFocusL [x,y] = showString "[ " . x . showString "]⊢ " . y
+  template JFocusR [x,y] = x . showString "⊢[ " . y . showString "] "
+  template Down    [x]   = showString "· " . x . showString "· "
+  template Comma   [x,y] = x . showString ", " . y
+
+
+-- * ASCII printing
+
+newtype ASCII a = ASCII a
+
+instance ToString (ASCII ConId) where
+  toString (ASCII (PosAtom x)) = x
+  toString (ASCII (NegAtom x)) = x ++ "'"
+  toString (ASCII F0L)     = "0" ; toString (ASCII F0R)     = "0" ; toString (ASCII FBox)  = "[]"
+  toString (ASCII F1L)     = "1" ; toString (ASCII F1R)     = "1" ; toString (ASCII FDia)  = "<>"
+  toString (ASCII FProd)   = "*" ; toString (ASCII FImpR)   = "->"; toString (ASCII FImpL) = "<-"
+  toString (ASCII SProd)   = "*" ; toString (ASCII SImpR)   = "->"; toString (ASCII SImpL) = "<-"
+  toString (ASCII HProd)   = "o" ; toString (ASCII HImpR)   = "-o"; toString (ASCII HImpL) = "o-"
+  toString (ASCII FPlus)   = "+" ; toString (ASCII FSubL)   = "<="; toString (ASCII FSubR) = "=>"
+  toString (ASCII SPlus)   = "+" ; toString (ASCII SSubL)   = "<="; toString (ASCII SSubR) = "=>"
+  toString (ASCII S0L)     = "0" ; toString (ASCII S0R)     = "0" ; toString (ASCII SBox)  = "[]"
+  toString (ASCII S1L)     = "1" ; toString (ASCII S1R)     = "1" ; toString (ASCII SDia)  = "<>"
+  toString (ASCII JAlgebr) = "|-"; toString (ASCII JStruct) = "|-"
+  toString (ASCII JFocusL) = "|-"; toString (ASCII JFocusR) = "|-"
+  toString (ASCII Down)    = "." ; toString (ASCII Comma)   = ","
+
+
+-- * Proofs
+
+type Proof = Term RuleId Void
+
+data Result
+  = Solved                 (Term ConId Void) Proof
+  | Parsed String [String] (Term ConId Void) Proof
+  deriving (Show)
diff --git a/CG/Parser.hs b/CG/Parser.hs
new file mode 100644
--- /dev/null
+++ b/CG/Parser.hs
@@ -0,0 +1,82 @@
+{-# LANGUAGE TupleSections, RecordWildCards #-}
+module CG.Parser (parse) where
+
+
+import           Prelude hiding (lex)
+import           CG.Base
+import           Control.Arrow (first)
+import           Control.Parallel.Strategies
+import           Data.List (nub)
+import           Data.Map (Map)
+import qualified Data.Map as M
+import           Data.Void (Void)
+
+
+
+-- * Parsing
+
+-- |Create all possible structures from a list of formulas, joining
+--  them with the binary structural connective @·⊗·@, and then find
+--  all proofs for each of these structures, returning a list of
+--  structures paired with their proofs.
+--  Note: the resulting list may contain pairs for structures for
+--  which no proofs were found.
+parse :: System ConId                 -- ^ Inference system
+       -> Int                          -- ^ Search depth
+       -> Map String (Term ConId Void) -- ^ Lexicon
+       -> String                       -- ^ Sentence
+       -> Term ConId Void              -- ^ Goal formula
+       -> [(Term ConId Void,Term RuleId Void)]
+parse sys@System{..} d lex sent g =
+  solve sys d judgements `using` parList rdeepseq
+  where
+    -- read the entries from the lexicon, wrapping them in a
+    -- down constructor if the logic is structural
+    entries = lookupAll lex (words sent)
+    entries'
+      | structural = map (unary Down) entries
+      | otherwise  = entries
+
+    -- construct the left-hand sides using the @brackets@ function
+    leftHandSides = brackets (unary <$> unaryOp) (binary (unsafeBinaryOp sys)) entries'
+
+    -- construct all possible judgements by combining them with
+    -- the sequent and the goal formula
+    sequent    = if structural then JFocusR else JAlgebr
+    judgements = map (flip (binary sequent) g) leftHandSides
+
+
+
+-- |Look up all words in a given list of words in a lexicon.
+lookupAll :: Map String (Term ConId Void) -- ^ Lexicon
+          -> [String]                     -- ^ Sentence
+          -> [Term ConId Void]
+lookupAll _   [    ] = []
+lookupAll lex (w:ws) = case M.lookup w lex of
+  Just tm -> tm : lookupAll lex ws
+  Nothing -> error ("Cannot find `"++w++"' in the lexicon.")
+
+
+
+-- |Generate all binary trees with n nodes, formed by applications of
+--  a given binary operator, with at most one application of a given
+--  unary operator at every node.
+brackets :: (Eq a) => Maybe (a -> a) -> (a -> a -> a) -> [a] -> [a]
+brackets mbPre op = nub . brack where
+
+  brack [ ] = [ ]
+  brack [x] = [x]
+  brack lst = maybe (go id) (\pre -> go id ++ go pre) mbPre
+    where
+      go f = [ f (l `op` r) | (ls,rs) <- split lst, l <- brack ls, r <- brack rs ]
+
+  split [_]    = []
+  split (x:xs) = ([x],xs) : map (first (x:)) (split xs)
+
+
+-- |Retrieve the single binary connective from the system, or throw an error.
+unsafeBinaryOp :: System c -> c
+unsafeBinaryOp System{..} = case binaryOp of
+  [   ] -> error "Must set at least one binary operator to parse."
+  [ f ] -> f
+  (_:_) -> error "Parsing with multiple binary operators is not implemented."
diff --git a/CG/Parsing.hs b/CG/Parsing.hs
new file mode 100644
--- /dev/null
+++ b/CG/Parsing.hs
@@ -0,0 +1,330 @@
+{-# LANGUAGE RecordWildCards, RankNTypes, TupleSections, ScopedTypeVariables #-}
+module CG.Parsing (readSystem
+                  ,readLexicon
+                  ,parseGoal
+                  ,formula
+                  ,structure
+                  ,judgement
+                  ,getCgHome
+                  )where
+
+
+import           CG.Base
+import           Control.Exception (IOException, handle)
+import           Data.Char (isSpace)
+import           Data.List (nub,isPrefixOf)
+import           Data.Void (Void)
+import           Data.Map (Map)
+import qualified Data.Map as M
+import           Text.Parsec hiding (option)
+import           Text.Parsec.Expr
+import           Text.Parsec.Error (setErrorPos)
+import           Text.Parsec.String (Parser)
+import           Text.Parsec.Language (LanguageDef,haskellStyle)
+import           Text.Parsec.Token (TokenParser,GenTokenParser(..),GenLanguageDef(..),makeTokenParser)
+import           System.Directory (doesFileExist)
+import           System.Environment (getEnv)
+import           System.FilePath ((</>))
+
+
+-- * Variable Parsing
+
+class VarParser v where
+  formulaVar   :: Parser v
+  structureVar :: Parser v
+
+instance VarParser Void where
+  formulaVar   = oneOf "ABCD" *> unexpected "Variables {A,B,C,D} are not allowed."
+  structureVar = oneOf "XYZW" *> unexpected "Variables {X,Y,Z,W} are not allowed."
+
+instance VarParser Char where
+  formulaVar   = lexeme cg (oneOf "ABCD") <?> "formula variable"
+  structureVar = lexeme cg (oneOf "XYZW") <?> "structure variable"
+
+
+-- * Language Definition
+
+cgDef :: LanguageDef st
+cgDef = haskellStyle
+  { identStart    = identLetter cgDef
+  , identLetter   = satisfy (\c -> not (isSpace c || c `elem` "()"))
+  , opStart       = opLetter cgDef
+  , opLetter      = oneOf "()"
+  , reservedNames = let
+
+    reservedNames   = ["where","and","atomic","positive","negative"]
+    reservedOpNames = nub (map toString operators ++ map (toString . ASCII) operators)
+    operators       = concat [unaryLogical ,unaryStructural
+                             ,binaryLogical,binaryStructural
+                             ,sequents, [Down]]
+
+    in reservedNames ++ reservedOpNames
+  }
+
+cg :: TokenParser st
+cg = makeTokenParser cgDef
+
+
+-- * Term Parsing
+
+con :: ConId -> Parser ()
+con c = reserved (toString c) <|> reserved (toString (ASCII c))
+  where
+    TokenParser{..} = cg
+
+con' :: ConId -> Parser ()
+con' c = do symbol (toString c) <|> symbol (toString (ASCII c)); return ()
+  where
+    TokenParser{..} = cg
+
+infl c = Infix   (con c *> return (binary c)) AssocLeft
+infr c = Infix   (con c *> return (binary c)) AssocRight
+pref c = Prefix  (con c *> return (unary  c))
+post c = Postfix (con c *> return (unary  c))
+
+
+atom :: Parser (Term ConId v)
+atom = do
+  let TokenParser{..} = cg
+  x <- identifier
+  return . nullary $
+    if last x `elem` "⁻'"
+      then NegAtom (init x)
+      else PosAtom       x
+
+
+formulaWithVar :: Parser (Term ConId Char)
+formulaWithVar = formula
+
+formula :: VarParser v => Parser (Term ConId v)
+formula =
+  buildExpressionParser table (parens formula <|> fvar <|> atom)
+  where
+    TokenParser{..} = cg
+    fvar  = Var <$> formulaVar
+    table =
+      [ [ pref F0L   , post F0R   , pref FBox
+        , pref F1L   , post F1R   , pref FDia  ]
+      , [ infl FSubL , infl FImpL , infl HImpL
+        , infr FSubR , infr FImpR , infr HImpR ]
+      , [ infr FProd , infl FPlus , infr HProd ]
+      ]
+
+
+structureWithVar :: Parser (Term ConId Char)
+structureWithVar = structure
+
+structure :: VarParser v => Parser (Term ConId v)
+structure =
+  buildExpressionParser table (parens structure <|> sdia <|> sbox <|> svar <|> down)
+  where
+    TokenParser{..} = cg
+
+    svar    = Var <$> structureVar
+    down    = unary Down <$> cdots formula <?> "down operator"
+    sdia    = unary SDia <$> (angles structure <|> rangles structure)
+    sbox    = unary SBox <$> (brackets structure)
+    cdots   = between (con Down)   (con Down)
+    rangles = between (symbol "⟨") (symbol "⟩")
+    table   =
+      [ [ pref S0L   , post S0R   , pref S1L   , post S1R   ]
+      , [ infl SSubL , infl SImpL , infr SSubR , infr SImpR ]
+      , [ infr SProd , infl SPlus ]
+      , [ infr Comma ]
+      ]
+
+
+judgementWithVar :: Parser (Term ConId Char)
+judgementWithVar = judgement
+
+judgement :: VarParser v => Parser (Term ConId v)
+judgement =
+  spaces *> (try (try jstruct <|> (try jfocusl <|> jfocusr)) <|> jalgebr)
+  where
+    TokenParser{..} = cg
+
+    jstruct = binary JStruct <$> structure        <* con' JStruct <*> structure
+    jfocusl = binary JFocusL <$> brackets formula <* con' JFocusL <*> structure
+    jfocusr = binary JFocusR <$> structure        <* con' JFocusL <*> brackets formula
+    jalgebr = binary JAlgebr <$> formula          <* con' JAlgebr <*> formula
+
+
+lexicon :: Parser (Map String (Term ConId Void))
+lexicon = whiteSpace >> M.fromList <$> many1 entry
+  where
+    TokenParser{..} = cg
+    entry = (,) <$> identifier <* symbol ":" <*> formula
+
+
+guard' :: Parser (Term ConId Char -> Guard ConId)
+guard' =
+  do reserved "where"
+     gs <- sepBy1 single (reserved "and")
+     if null gs
+       then unexpected "panic!"
+       else return (foldr1 and gs)
+  where
+    TokenParser{..} = cg
+    and f g x = f x `And` g x
+    single    = predicate <*> formulaVar
+    predicate = choice
+      [ reserved "atomic"   *> return atomic
+      , reserved "positive" *> return positive
+      , reserved "negative" *> return negative
+      ]
+
+
+rule :: Parser (Rule ConId Int)
+rule = do
+  n  <- identifier
+  _  <- symbol ":"
+  js <- sepBy1 judgement sep
+
+  let ps   = init js
+  let c    = last js
+  let rule = mkRule n ps c
+
+  mb <- optionMaybe guard'
+  return $
+    case mb of
+     Just mk -> rule { guard = mk c }
+     _       -> rule
+
+  where
+    TokenParser{..} = cg
+    sep = symbol "→" <|> symbol "-->"
+
+
+option :: Parser Option
+option = do
+  symbol "set"
+  choice (map try
+    [ symbol "finite"      *> return (IsFinite True)
+    , symbol "infinite"    *> return (IsFinite False)
+    , symbol "algebraic"   *> return (IsStructural False)
+    , symbol "structural"  *> return (IsStructural True)
+    , symbol "agda_name"   *> symbol "=" *> (AgdaName   <$> many1 (satisfy (not . isSpace)))
+    , symbol "agda_module" *> symbol "=" *> (AgdaModule <$> many1 (satisfy (not . isSpace)))
+    , symbol "parse_with"  *> symbol "=" *> (ParseWith  <$> pParseWith)
+    ])
+    <?> "option"
+    where
+      TokenParser{..} = cg
+      pParseWith :: Parser [ParseWith]
+      pParseWith = many1 (useBinary <|> useUnary)
+        where
+          useOp opt = choice . map (\c -> con c >> return (opt c))
+          useUnary  = useOp UseUnary  (unaryLogical  ++ unaryStructural)
+          useBinary = useOp UseBinary (binaryLogical ++ binaryStructural)
+
+
+-- * Options
+
+data Option
+  = IsFinite Bool
+  | IsStructural Bool
+  | ParseWith [ParseWith]
+  | AgdaName String
+  | AgdaModule String
+  deriving Show
+
+data ParseWith
+  = UseUnary ConId
+  | UseBinary ConId
+  deriving Show
+
+
+-- |Handle options for proof systems.
+runOptions :: [Option] -> System ConId
+runOptions = postProcess . foldr runOption emptySystem
+  where
+    runOption (IsFinite     b) s = s { finite     = b }
+    runOption (IsStructural b) s = s { structural = b }
+    runOption (AgdaName     n) s = s { agdaName   = Just n }
+    runOption (AgdaModule   n) s = s { agdaModule = Just n }
+    runOption (ParseWith    x) s = foldr runPW s x
+
+    runPW (UseUnary  op) = addUnary  op
+    runPW (UseBinary op) = addBinary op
+
+    postProcess sys@System{..}
+      | structural = sys { unaryOp  = fmap toStructural unaryOp
+                         , binaryOp = fmap toStructural binaryOp }
+      | otherwise  = sys
+
+
+-- * Parsers
+
+parseGoal :: String -> IO (Term ConId Void)
+parseGoal str = case parse formula "" str of
+  Left  e -> fail ("Could not parse goal formula `"++show str++"'.\n"++show e)
+  Right x -> return x
+
+getCgHome :: IO (Maybe String)
+getCgHome =
+  handle (\(e :: IOException) -> return Nothing) (Just <$> getEnv "CGTOOL_HOME")
+
+readLexicon :: FilePath -> IO (Map String (Term ConId Void))
+readLexicon lexiconFile = do
+  fileExist <- doesFileExist lexiconFile
+  if fileExist
+    then unsafeReadLexicon lexiconFile
+    else do mbHome <- getCgHome
+            case mbHome of
+             Just home -> do
+               let lexiconFile' = home </> "lex" </> lexiconFile
+               fileExist' <- doesFileExist lexiconFile'
+               if fileExist'
+                 then unsafeReadLexicon lexiconFile'
+                 else error ("No such lexicon `" ++ lexiconFile ++ "'")
+             Nothing   -> error ("No such lexicon `" ++ lexiconFile ++ "'")
+
+unsafeReadLexicon :: FilePath -> IO (Map String (Term ConId Void))
+unsafeReadLexicon lexiconFile = do
+  lexiconContent <- readFile lexiconFile
+  case parse lexicon lexiconFile lexiconContent of
+   Left  e -> fail ("Could not parse lexicon.\n"++show e)
+   Right l -> return l
+
+readSystem :: FilePath -> IO (System ConId)
+readSystem systemFile = do
+  fileExist <- doesFileExist systemFile
+  if fileExist
+    then unsafeReadSystem systemFile
+    else do mbHome <- getCgHome
+            case mbHome of
+             Just home -> do
+               let systemFile' = home </> "sys" </> systemFile
+               fileExist' <- doesFileExist systemFile'
+               if fileExist'
+                 then unsafeReadSystem systemFile'
+                 else error ("No such system `" ++ systemFile ++ "'")
+             Nothing   -> error ("No such system `" ++ systemFile ++ "'")
+
+
+unsafeReadSystem :: FilePath -> IO (System ConId)
+unsafeReadSystem systemFile = go <$> readFile systemFile
+  where
+    go contents = sys { rules = rules }
+      where
+        TokenParser{..} = cg
+
+        (rawOpts,rawRules)
+          = span (isOption . snd)            -- break at first non-option
+            $ filter (not . isComment . snd) -- filter out all comments
+            $ zip [1..]                      -- add line numbers
+            $ lines contents                 -- split lines
+
+        opts  = map (parseOrError option systemFile) rawOpts
+        rules = map (parseOrError rule   systemFile) rawRules
+        sys   = runOptions opts
+
+        isOption  ln = "set" `isPrefixOf` ln
+        isComment ln = case parse (whiteSpace *> eof) "" ln of
+          Left  _ -> False
+          Right _ -> True
+
+    parseOrError :: Parser a -> FilePath -> (Line, String) -> a
+    parseOrError p fn (n,str) = case parse p fn str of
+      Left  e -> error (show (setErrorPos (setSourceLine (errorPos e) n) e))
+      Right x -> x
diff --git a/CG/Prover.hs b/CG/Prover.hs
new file mode 100644
--- /dev/null
+++ b/CG/Prover.hs
@@ -0,0 +1,85 @@
+{-# LANGUAGE GADTs, FlexibleInstances, FlexibleContexts, MultiParamTypeClasses,
+    UndecidableInstances, DeriveGeneric, RecordWildCards, TupleSections #-}
+module CG.Prover (module X,System(..),solve,findAll,findFirst) where
+
+
+import CG.Prover.Base as X
+import CG.Prover.Ins  as X
+import Data.Hashable       (Hashable(..))
+import Data.HashSet   as S (insert,member,empty)
+import Data.Maybe          (mapMaybe)
+import Data.Void           (Void)
+
+
+-- |Search for proofs of the given goals using the given system, using
+--  either breadth-first search (for finite systems) or depth-limited
+--  interleaved breadth-first search (for infinite systems).
+--  Note: this algorithm performs loop-checking under the assumption
+--  that /unary/ rules may cause loops, and rules of other arities
+--  make progress.
+solve :: (Operator c, Guardable c, Hashable c, Ord c) => System c -> Int -> [Term c Void] -> [(Term c Void, Term String Void)]
+solve System{..} depth goals
+  | finite    = concatMap (\goal -> map (goal,) (findAll goal rules)) goals
+  | otherwise = findFirst depth goals rules
+
+
+-- |Search for proofs of the given goal using the gives rules using
+--  breadth-first search.
+--  Note: this algorithm performs loop-checking under the assumption
+--  that /unary/ rules may cause loops, and rules of other arities
+--  make progress.
+findAll :: (Operator c, Guardable c, Hashable c, Ord c) => Term c Void -> [Rule c Int] -> [Term String Void]
+findAll goal rules = slv [(S.empty,[goal],head)] []
+  where
+    slv [                    ] [ ] = []
+    slv [                    ] acc = slv (reverse acc) []
+    slv ((_   ,  [],prf):prfs) acc = prf [] : slv prfs acc
+    slv ((seen,g:gs,prf):prfs) acc
+      | S.member g seen = slv prfs acc
+      | otherwise       = slv prfs (mapMaybe step rules ++ acc)
+      where
+        step (Rule n grd a ps c) =
+          if runGuard grd g
+          then do s <- runIns (ins g c)
+                  let prf'  = prf . build n a
+                  let seen' | a == 1    = S.insert g seen
+                            | otherwise = S.empty
+                  ps' <- mapM (subst s) ps
+                  return (seen', ps' ++ gs, prf')
+          else fail ("Cannot apply rule `"++n++"'")
+
+
+-- |Search for proofs of the given goal using the gives rules using
+--  depth-limited breadth-first search.
+--  Note: this algorithm performs loop-checking under the assumption
+--  that /unary/ rules may cause loops, and rules of other arities
+--  make progress.
+findFirst :: (Guardable c, Hashable c, Ord c)
+          => Int           -- ^ Search Depth
+          -> [Term c Void] -- ^ Goal Terms
+          -> [Rule c Int]  -- ^ Inference rules
+          -> [(Term c Void, Term String Void)]
+findFirst d goals rules = slv (d + 1) (fmap (\g -> (S.empty,g,[g],head)) goals) []
+  where
+    slv 0                        _   _ = []
+    slv _ [                      ] [ ] = []
+    slv d [                      ] acc = slv (d - 1) (reverse acc) []
+    slv _ ((_   ,o,  [],prf):_   ) _   = [(o, prf [])]
+    slv d ((seen,o,g:gs,prf):prfs) acc
+      | S.member g seen = slv d prfs acc
+      | otherwise       = slv d prfs (mapMaybe step rules ++ acc)
+      where
+        step (Rule n grd a ps c) =
+          if runGuard grd g
+          then do s <- runIns (ins g c)
+                  let prf'  = prf . build n a
+                  let seen' | a == 1    = S.insert g seen
+                            | otherwise = S.empty
+                  ps' <- mapM (subst s) ps
+                  return (seen', o, ps' ++ gs, prf')
+          else fail ("Cannot apply rule `"++n++"'")
+
+
+-- |Build a proof by adding a new constructor.
+build :: r -> Int -> [Term r Void] -> [Term r Void]
+build n a ts = let (xs,ys) = splitAt a ts in Con n xs : ys
diff --git a/CG/Prover/Base.hs b/CG/Prover/Base.hs
new file mode 100644
--- /dev/null
+++ b/CG/Prover/Base.hs
@@ -0,0 +1,226 @@
+{-# LANGUAGE GADTs, RankNTypes, FlexibleInstances, FlexibleContexts,
+    UndecidableInstances, DeriveGeneric, DeriveFunctor, DeriveFoldable,
+    DeriveTraversable, StandaloneDeriving, RecordWildCards #-}
+module CG.Prover.Base where
+
+
+import Control.Monad.State (MonadState(..),evalState)
+import Control.DeepSeq     (NFData)
+import Data.Char           (ord)
+import Data.Hashable       (Hashable)
+import Data.Serialize      (Serialize)
+import Data.IntMap as IM   (IntMap,lookup,empty,insert)
+import Data.List           (intersperse)
+import Data.Void           (Void,absurd)
+import Data.Void.Unsafe    (unsafeVacuous)
+import GHC.Generics        (Generic)
+
+
+-- * Special Show instance for String
+
+class    ToString a      where toString :: a -> String
+instance ToString Bool   where toString = (++" ") . show
+instance ToString Int    where toString = (++" ") . show
+instance ToString Void   where toString = absurd
+instance ToString String where toString = (++" ")
+instance ToString Char   where toString = (:" ")
+
+
+-- * Terms
+
+data Term c v where
+  Var :: ! v               -> Term c v
+  Con :: ! c -> [Term c v] -> Term c v
+  deriving (Eq,Ord,Generic)
+
+
+deriving instance Functor (Term c)
+deriving instance Foldable (Term c)
+deriving instance Traversable (Term c)
+instance (Hashable  c, Hashable  v) => Hashable  (Term c v)
+instance (NFData    c, NFData    v) => NFData    (Term c v)
+instance (Serialize c, Serialize v) => Serialize (Term c v)
+
+
+-- |A class which defines a printable operator. The @prec@ function
+--  returns the precedence of the operator. The @template@ function
+--  is a generalisation of the fixity, where the operator can be
+--  anything that knows how to print itself.
+class Operator a where
+  prec     :: a -> Int
+  template :: a -> ([ShowS] -> ShowS)
+
+
+instance Operator String where
+  prec     _    = 0
+  template x [] = showString x
+  template x xs =
+    showParen True (foldr (.) id (intersperse (showChar ' ') (showString x : xs)))
+
+
+instance (Operator c, ToString v) => Show (Term c v) where
+  showsPrec _ (Var i)    =
+    showString (toString i)
+  showsPrec p (Con x xs)
+    | p > 0 && q > 0 && p >= q = showString "( " . ret . showString ") "
+    | otherwise                = ret
+    where
+      q   = prec x
+      ret = template x (map (showsPrec q) xs)
+
+
+-- * Guards
+
+class (Eq c) => Guardable c where
+  isAtomic   :: Term c v -> Bool
+  isPositive :: Term c v -> Bool
+  isNegative :: Term c v -> Bool
+
+
+data Guard c
+  = Any
+  | Atomic   (Term c Bool)
+  | Positive (Term c Bool)
+  | Negative (Term c Bool)
+  | And (Guard c) (Guard c)
+  deriving (Eq,Ord,Show,Generic)
+
+
+instance (Hashable  c) => Hashable  (Guard c)
+instance (NFData    c) => NFData    (Guard c)
+instance (Serialize c) => Serialize (Guard c)
+
+
+-- |Construct a given primitive guard, together with its arguments, into a
+--  guarding function. Used internally in @runGuard@.
+mkGuard :: (Guardable c)
+           => (forall v'. Term c v' -> Bool)
+           -> Term c Bool
+           -> (forall v'. Term c v' -> Bool)
+mkGuard _      _     (Var _)             = True
+mkGuard p (Var True)      y              = p y
+mkGuard _ (Var _   )      _              = True
+mkGuard p (Con x xs) (Con y ys) | x == y = and (zipWith (mkGuard p) xs ys)
+mkGuard _      _          _              = False
+
+
+-- |Run a guard, checking if the given Term has all the desired properties.
+runGuard :: (Guardable c) => Guard c -> (forall v. Term c v -> Bool)
+runGuard  Any         = const True
+runGuard (Atomic   c) = mkGuard isAtomic   c
+runGuard (Positive c) = mkGuard isPositive c
+runGuard (Negative c) = mkGuard isNegative c
+runGuard (gd `And` gd2) = \x -> runGuard gd x && runGuard gd2 x
+
+
+-- |Smart constructors for guards.
+atomic, positive, negative :: (Eq v) => v -> Term c v -> Guard c
+atomic   x = Atomic   . fmap (==x)
+positive x = Positive . fmap (==x)
+negative x = Negative . fmap (==x)
+
+
+-- * Rules
+
+type RuleId = String
+
+data Rule c v = Rule
+  { name       :: ! RuleId
+  , guard      :: ! (Guard c)
+  , arity      :: ! Int
+  , premises   :: ! [Term c v]
+  , conclusion :: ! (Term c v)
+  }
+  deriving (Eq,Ord,Generic)
+
+
+deriving instance Functor (Rule c)
+deriving instance Foldable (Rule c)
+deriving instance Traversable (Rule c)
+instance (Hashable  c, Hashable  v) => Hashable  (Rule c v)
+instance (NFData    c, NFData    v) => NFData    (Rule c v)
+instance (Serialize c, Serialize v) => Serialize (Rule c v)
+
+
+-- |Construct a @Rule@ from a @RuleId@, a list of premises and a conclusion.
+mkRule :: RuleId -> [Term c Char] -> Term c Char -> Rule c Int
+mkRule n ps c = Rule n Any (length ps) ps' c'
+  where
+    (c' : ps') = evalState (mapM (mapM label) (c : ps)) (0, IM.empty)
+
+    label x =
+      do (i, vm) <- get
+         case IM.lookup (ord x) vm of
+          Just j -> return j
+          _      -> do put (i + 1, IM.insert (ord x) i vm); return i
+
+
+
+instance (Show c, ToString v, Show (Term c v)) => Show (Rule c v) where
+  showsPrec _ (Rule n g _ ps c) =
+    (showString (n++" : ")) .
+    (foldr1 (.) (intersperse (showString "→ ") (map shows (ps ++ [c]))))
+
+
+-- * Substitutions
+
+type VMap c v = IntMap (Term c v)
+
+
+-- |Apply the given variable map to a given term. Note: the variable
+--  map has to contain a term for every variable used in the given
+--  term. The resulting term will be variable-free.
+subst :: VMap c Void -> Term c Int -> Maybe (Term c Void)
+subst s = app where
+
+  app (Con x xs) = Con x <$> mapM app xs
+  app (Var i   ) = IM.lookup i s
+
+
+-- * Systems
+
+data System c = System
+  { finite     :: Bool
+  , structural :: Bool
+  , rules      :: [Rule c Int]
+
+    -- options related to parsing
+  , unaryOp    :: Maybe c
+  , binaryOp   :: [c]
+
+    -- options related to Agda generation
+  , agdaName   :: Maybe String
+  , agdaModule :: Maybe String
+  }
+  deriving (Eq,Ord,Show,Generic)
+
+
+instance (Hashable  c) => Hashable  (System c)
+instance (NFData    c) => NFData    (System c)
+instance (Serialize c) => Serialize (System c)
+
+
+-- |The minimal system. All it is missing is a binary operator.
+emptySystem :: System c
+emptySystem = System
+  { finite     = False
+  , structural = False
+  , rules      = []
+
+  , unaryOp    = Nothing
+  , binaryOp   = []
+
+  , agdaName   = Nothing
+  , agdaModule = Nothing
+  }
+
+addUnary :: c -> System c -> System c
+addUnary op sys = case unaryOp sys of
+  Nothing -> sys { unaryOp = Just op }
+  Just _  -> error "Cannot parse using more than one unary operator."
+
+addBinary :: c -> System c -> System c
+addBinary op sys@System{..} = sys { binaryOp = binaryOp ++ [op] }
+
+addRule :: Rule c Int -> System c -> System c
+addRule rule sys@System{..} = sys { rules = rules ++ [rule] }
diff --git a/CG/Prover/Ins.hs b/CG/Prover/Ins.hs
new file mode 100644
--- /dev/null
+++ b/CG/Prover/Ins.hs
@@ -0,0 +1,32 @@
+module CG.Prover.Ins (Ins,runIns,ins) where
+
+
+import Control.Monad.State (MonadState(..),StateT,execStateT,liftM,liftM2)
+import Data.IntMap as IM (lookup,empty,insert)
+import Data.Void (Void)
+import CG.Prover.Base
+
+
+type Ins c a = StateT (VMap c Void) Maybe a
+
+
+runIns :: Ins c a -> Maybe (VMap c Void)
+runIns x = execStateT x IM.empty
+
+
+ins :: (Eq c) => Term c Void -> Term c Int -> Ins c (Term c Void)
+ins   (Con x xs) (Con y ys) | x == y = liftM (Con x) (insAll xs ys)
+ins x@(Con _ _ ) (Var i   )          = do vm <- get
+                                          case IM.lookup i vm of
+                                           Just y -> if x == y
+                                                     then return x
+                                                     else fail "cannot insantiate"
+                                           _      -> do put (IM.insert i x vm)
+                                                        return x
+ins _            _                   = fail "cannot insantiate"
+
+
+insAll :: (Eq c) => [Term c Void] -> [Term c Int] -> Ins c [Term c Void]
+insAll    []     []  = return []
+insAll (x:xs) (y:ys) = liftM2 (:) (ins x y) (insAll xs ys)
+insAll  _      _     = fail "cannot instantiate"
diff --git a/CG/ToAgda.hs b/CG/ToAgda.hs
new file mode 100644
--- /dev/null
+++ b/CG/ToAgda.hs
@@ -0,0 +1,176 @@
+{-# LANGUAGE RecordWildCards, FlexibleContexts #-}
+module CG.ToAgda (Result(..),writeAgdaFile) where
+
+
+import           CG.Base
+import           Control.Monad.State (State,get,put,runState)
+import           Data.Char (isSpace,toUpper,toLower)
+import           Data.List (intersperse,intercalate)
+import           Data.Map (Map)
+import qualified Data.Map as M
+import           Data.Maybe (fromMaybe)
+import           Data.Void (Void)
+import           System.IO
+import           Text.Printf (printf)
+
+
+
+toCtxt :: System c -> String -> String
+toCtxt sys@System{..} sent
+  | structural = unwords (intersperse "," (words sent ++ ["∅"]))
+  | otherwise  = unwords (intersperse "," (words sent))
+
+toAgdaName :: System c -> String
+toAgdaName System{..} = case agdaName of
+  Just n -> n
+  _      -> error "Must set agda_name to export to Agda."
+
+toAgdaModule :: System c -> String
+toAgdaModule System{..} = case agdaModule of
+  Just n -> n
+  _      -> error "Must set agda_module to export to Agda."
+
+toBaseName :: Result -> String
+toBaseName (Solved     g _) = defaultName g
+toBaseName (Parsed s _ _ _) = map toLower (sanitise s)
+
+sanitise [] = []
+sanitise (' ':' ': xs) = sanitise (' ':xs)
+sanitise (' '    : xs) = '_' : sanitise xs
+sanitise ('.'    : xs) = sanitise xs
+sanitise (':'    : xs) = sanitise xs
+sanitise ( c     : xs) = toUpper c : sanitise xs
+
+sanitiseForLaTeX [] = []
+sanitiseForLaTeX ('_':xs) = '\\' : '_' : sanitiseForLaTeX xs
+sanitiseForLaTeX ( c :xs) =         c  : sanitiseForLaTeX xs
+
+defaultName :: (Show v, ToString v) => Term ConId v -> String
+defaultName = map repl . filter (not . isSpace) . show
+  where
+    repl '(' = '['
+    repl ')' = ']'
+    repl  c  =  c
+
+withType :: (Show v, ToString v) => Term ConId v -> String -> String
+withType = printf "id {A = ⟦ %s ⟧ᵀ} (%s)" . show
+
+agdaList :: [String] -> String
+agdaList = unwords . intersperse "\n  ∷" . (++["[]"])
+
+agdaList' :: [String] -> String
+agdaList' = unwords . intersperse " ∷" . (++["[]"])
+
+toAgdaDefn :: System c -> Term ConId Void -> Result -> State (Map String Int) String
+toAgdaDefn sys goalType ret = case ret of
+  (Solved     g p) ->
+    return $ unlines
+      [ baseName++" : "++dataTypeName++" "++show g
+      , baseName++" = "++show p
+      , ""
+      ]
+  (Parsed s e g p) -> do
+    n <- next s; let subn = sub n
+    return . unlines $
+      [ synBaseName++subn++" : "++dataTypeName++" "++show g
+      , synBaseName++subn++" \n  = "++show p
+      , semBaseName++subn++" : ⟦ "++show goalType++" ⟧ᵀ"
+      , semBaseName++subn++" \n  = [ "++synBaseName++subn++" ]ᵀ ("++toCtxt sys s++")"
+      , ""
+      ]
+      ++
+      (if null e then [] else
+      [ listBaseName++subn++" : List Term"
+      , listBaseName++subn++" \n  = "++agdaList (map (\x -> "quoteTerm ("++withType goalType x++")") e)
+      , testBaseName++subn++" : Assert (quoteTerm "++semBaseName++subn++" ∈ "++listBaseName++subn++")"
+      , testBaseName++subn++" = _"
+      , ""
+      ])
+      ++
+      [""]
+  where
+    baseName     = toBaseName ret
+    synBaseName  = map toUpper baseName
+    semBaseName  = map toLower baseName
+    listBaseName = "LIST_"++baseName
+    testBaseName = "TEST_"++baseName
+    dataTypeName = toAgdaName sys
+
+
+-- |Return a valid Agda file given a sequence of proofs.
+writeAgdaFile :: Handle -> String -> System c -> [Result] -> Term ConId Void -> IO [String]
+writeAgdaFile h moduleName sys@System{..} prfs goalType = do
+
+  let (proofDefn, nameMap) =
+        runState (mapM (toAgdaDefn sys goalType) prfs) M.empty
+  let nameList = toNameList nameMap
+  let fileList = map (\(i,s) -> map toLower (sanitise s) ++ "_" ++ show i) nameList
+
+  mapM_ (hPutStrLn h) $
+    [ "------------------------------------------------------------------------"
+    , "-- The Lambek Calculus in Agda"
+    , "------------------------------------------------------------------------"
+    , ""
+    , "open import Data.Colist using (fromList)"
+    , "open import Data.Bool   using (Bool; true; false; _∧_; _∨_)"
+    , "open import Data.List   using (List; _∷_; [])"
+    , "open import Data.String using (String)"
+    , "open import Data.Vec    using (_∷_; [])"
+    , "open import Function    using (id)"
+    , "open import IO          using (IO; mapM′; run)"
+    , "open import Reflection  using (Term)"
+    , "open import "++toAgdaModule sys
+    , ""
+    , "module "++moduleName++" where"
+    , ""
+    , unlines proofDefn
+    , ""
+    , "proofList : List Proof"
+    , "proofList\n  = " ++ (agdaList (proofList structural nameList))
+    , ""
+    , "main : _"
+    , "main = run (mapM′ writeProof (fromList proofList))"
+    ]
+
+  return fileList
+
+
+-- |Convert a given map of sentences to max IDs, to a list of names.
+toNameList :: Map String Int -> [(Int, String)]
+toNameList sentenceIds =
+  [(j,s) | (s,i) <- M.toList sentenceIds, j <- [0..i-1]]
+
+
+-- |Return a single list which contains all proofs as LaTeX strings.
+proofList :: Bool -> [(Int, String)] -> [String]
+proofList structural nameList = do
+  (i,s) <- nameList
+  let
+    fileName = map toLower (sanitise s) ++ "_" ++ show i
+    termName = map toUpper (sanitise s) ++ sub i
+    sentence = sanitiseForLaTeX (toUpper (head s) : map toLower (tail s) ++ ".")
+    wordList = if structural
+               then agdaList' (map (show . sanitiseForLaTeX) (words s))
+               else agdaList' [show (sanitiseForLaTeX (sanitise s))]
+  return $
+    printf "proof %s %s (toLaTeX %s) (toLaTeXTerm (%s) (toTerm %s))"
+    (show fileName) (show sentence) termName wordList termName
+
+
+-- |Compute the next number for this String.
+next :: String -> State (Map String Int) Int
+next s = do m <- get
+            let n = fromMaybe 0 (M.lookup s m)
+            put (M.insert s (n + 1) m)
+            return n
+
+
+-- |Show a number in subscript.
+sub :: Int -> String
+sub = map toSub . show
+  where
+    toSub '0' = '₀'; toSub '5' = '₅'
+    toSub '1' = '₁'; toSub '6' = '₆'
+    toSub '2' = '₂'; toSub '7' = '₇'
+    toSub '3' = '₃'; toSub '8' = '₈'
+    toSub '4' = '₄'; toSub '9' = '₉'
diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,674 @@
+              GNU GENERAL PUBLIC LICENSE
+                Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
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+
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diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/cg.cabal b/cg.cabal
new file mode 100644
--- /dev/null
+++ b/cg.cabal
@@ -0,0 +1,30 @@
+name:                cg
+version:             0.0.9.0
+synopsis:            Parser for categorial grammars.
+description:         Parser for categorial grammars.
+stability:           experimental
+license:             GPL-3
+license-file:        LICENSE
+author:              Pepijn Kokke
+maintainer:          pepijn.kokke@gmail.com
+copyright:           (c) 2015 Pepijn Kokke
+category:            Language
+build-type:          Simple
+cabal-version:       >=1.10
+
+executable CG
+  main-is:             CG.hs
+  other-extensions:    RecordWildCards, TupleSections, OverloadedStrings,
+                       ViewPatterns, FlexibleContexts, PartialTypeSignatures,
+                       DeriveGeneric, TypeSynonymInstances, FlexibleInstances,
+                       GADTs, MultiParamTypeClasses, UndecidableInstances,
+                       RankNTypes
+  other-modules:       CG.Prover.Base, CG.Prover.Ins, CG.Prover,
+                       CG.Base, CG.Parsing, CG.Parser, CG.ToAgda
+  build-depends:       base >=4.8 && <4.9, bytestring, utf8-string, parallel >=3.2 && <3.3, 
+                       containers >=0.5 && <0.6, directory >=1.2 && <1.3,
+                       filepath >=1.4 && <1.5, parsec >=3.1 && <3.2,
+                       deepseq >=1.4 && <1.5, hashable >=1.2 && <1.3,
+                       unordered-containers >=0.2 && <0.3, mtl >=2.2 && <2.3,
+                       void >=0.7 && <0.8, cereal >= 0.4 && < 0.5, split, process, text
+  default-language:    Haskell2010
