diff --git a/LICENSE b/LICENSE
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+++ b/LICENSE
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+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
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+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,4 @@
+import Distribution.Simple
+main = defaultMain
+
+
diff --git a/caldims.cabal b/caldims.cabal
new file mode 100644
--- /dev/null
+++ b/caldims.cabal
@@ -0,0 +1,31 @@
+name:           caldims
+version:        0.1.0
+license:        GPL
+license-file:   LICENSE
+copyright:      Copyright (c) 2007 Marcel Manthe
+maintainer:	Rick Kaudewitz <rick.kaudewitz@yahoo.de>
+category:	Math
+stability:      experimental
+synopsis:       Calculation tool and library supporting units
+description:    CalDims is an easy to use tool for defining functions and units 
+                (basic and derrived), so it can provide dimension-save calculation
+                (not embedded but via shell).
+ghc-options:    -Wall -fno-warn-orphans
+exposed-Modules: 
+	Language.CalDims.Expression, 
+	Language.CalDims.Action,
+	Language.CalDims.Misc,
+	Language.CalDims.Program,
+	Language.CalDims.State,
+	Language.CalDims.Expr,
+	Language.CalDims.Helpers,
+	Language.CalDims.Texts,
+	Language.CalDims.Types
+build-depends:  base, haskell98, parsec, readline, mtl, containers, directory
+hs-source-dirs: src
+build-type: Simple
+
+executable:     caldims
+ghc-options:    -Wall -fno-warn-orphans
+main-is:        Main.hs
+hs-source-dirs: tool src
diff --git a/src/Language/CalDims/Action.hs b/src/Language/CalDims/Action.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Action.hs
@@ -0,0 +1,614 @@
+{-# LANGUAGE FlexibleInstances, CPP, MultiParamTypeClasses #-}
+module Language.CalDims.Action 
+	( Command (..)
+	, Result (..)
+	, Mon
+	, run
+	, eval
+	, doCall
+	, dependencies
+	, evalDimsPart
+	, process) where
+
+import Language.CalDims.Helpers
+import Language.CalDims.Types
+import Language.CalDims.Texts as Texts
+import Language.CalDims.State 
+import Language.CalDims.Expr ()
+
+import Control.Monad.State hiding (State)
+import qualified Control.Monad.State as SM
+import Control.Monad.Error
+import qualified Data.Map as Map
+import Data.Ratio
+import Data.List (nub)
+
+#ifdef DEBUG
+import Debug.Trace
+#endif
+
+data Command 
+	= AddFunction Name Args Expr 
+	| AddBasicUnit Name 
+	| AddUnit Name Expr 
+	| Echo String 
+	| Remove Name 
+	| RemoveCascade Name 
+	| Help
+	| Eval Expr Conversion
+	| EvalDimsPart Expr
+	| DebugExpr Expr 
+	| DebugName Name 
+	| DebugDependencies Name 
+	| GetState 
+	| WriteState String deriving Show
+
+instance Pretty Command where pretty = show
+
+data Result = Ok (Maybe String) | StringResult String | EvaledResult (R, Dims) | ExprResult Expr | DimsResult Dims | WriteStringToFile String String deriving Show
+instance Pretty Result where
+	pretty (Ok Nothing) = "ok."
+	pretty (Ok (Just s)) = "ok, but " ++ s
+	pretty (StringResult s) = s
+	pretty (EvaledResult (r, dims)) = let d = pretty dims in 
+		pretty r ++ (if null d then "" else " " ++ pretty dims)
+	pretty (DimsResult dims) = pretty dims
+	pretty (ExprResult e) = pretty e
+	pretty (WriteStringToFile _ fn) = "Writing state to " ++ fn ++ "."
+
+
+minEval :: Expr -> Mon (R, Dims)
+minEval e = do
+	x <- eval e
+	dims <- minDims (snd x)
+	convert x dims
+
+type Mon a = ErrorAndState String State a
+
+process :: Command -> Mon Result
+process (AddFunction n args expr) = insert n $ Function args expr
+process (AddBasicUnit n) = insert n $ BasicDimension
+process (AddUnit n expr) = insert n $ Dimension expr
+process (Echo s) = return $ StringResult s
+process (Remove n) = remove False n 
+process (RemoveCascade n) = remove True n 
+process Help = return $ StringResult (show Texts.helpText)
+process (Eval expr conv) = do
+	res <- eval expr
+	case conv of
+		Keep -> return $ EvaledResult res
+		Explicit dims -> do
+			res' <- convert res dims
+			return $ EvaledResult res'
+		InTermsOf tExpr -> do
+			r@(n,_) <- minEval tExpr
+			if (n==0) 
+				then fail "cannot express in terms of 0."
+				else do
+					r' <- minEval (Bin Div expr (Evaled r))
+					return $ ExprResult (Bin Mul (Evaled r') tExpr) 
+				-- FIXME: there are actually 3 ways to combine:
+				-- a/b b/a and a*b -> choose the simplest
+		Basic -> do
+			res' <- convertBasic res
+			return $ EvaledResult res'
+		Minimal -> do
+			dims <- minDims (snd res)
+			res' <- convert res dims
+			return $ EvaledResult res'
+
+process (EvalDimsPart expr) = do
+	res <- evalDimsPart expr
+	return $ DimsResult res
+process (DebugExpr expr) = return $ StringResult $ pretty expr
+process (DebugName n) = do
+	entry <- requireEntry n
+	return $ StringResult (pretty (n, entry))
+process (DebugDependencies n) = do
+	d <- dependencies n
+	r <- reverseDependencies n
+	return $ StringResult (unlines' [pretty d, pretty r])
+	
+process GetState = do
+	state <- get
+	return $ StringResult (pretty state)
+process (WriteState file) = do
+	state <- get
+	return $ WriteStringToFile (pretty state) file
+	
+
+instance Pretty State where --FIXME: the implementation might be too complex
+        pretty s = case (runState $ runErrorT f) s of
+                                (Left e, _) -> error e
+                                (Right l, _) -> unlines' l 
+		where 
+			f = do
+                        	state <- get
+	                        depList <- liftM nub $ liftM reverse $ liftM (filter (not . isBuiltin state)) $ liftM concat $ sequence $ map dependencies' (Map.keys $ getScope state)
+        	                mapM pretty' depList
+
+			pretty' :: Name -> Mon String
+			pretty' n = do
+				e <- requireEntry n
+				return $ pretty (n, e)
+
+
+remove :: Bool -> Name -> Mon Result
+remove casc n = do
+	rd <- reverseDependencies n
+	case (null rd, casc) of
+		(True, False) -> remove_ >> return (Ok Nothing)
+		(_, True) -> removeList_ (n:rd)  >> return (Ok Nothing)
+		(False, False) -> throwError $ "Please remove " ++ pretty rd ++ " first, or remove " ++ pretty n ++ " cascading."
+	where
+		remove_ = modi $ Map.delete n
+		removeList_ l = modi $ Map.filterWithKey (\x _ -> not $ x `elem` l)
+
+
+modi :: (Scope -> Scope) -> Mon ()
+modi f = modify (\x -> x {getScope = f (getScope x)})
+
+
+insert :: Name -> StateEntry -> Mon Result
+insert n newEntry = let 
+	doInsert = modi $ Map.insert n newEntry in do 
+        oldEntry <- getEntry n
+      	warn <- case oldEntry of
+                Nothing -> doInsert >> return Nothing
+                Just oldEntry_ -> do
+			i <- typeIsomorph newEntry oldEntry_
+			if i
+				then doInsert >> return (Just "an object has changed")
+				else throwError $ "There already is an object `" ++ pretty n ++ "` with another type."
+	return (Ok warn)
+
+
+dependencies' :: Name -> Mon [Name]
+dependencies' n = do
+	d <- dependencies n
+	return $ n:d
+
+
+dependencies :: Name -> Mon [Name]
+dependencies n = do
+	e <- requireEntry n
+	return $ nub $ case e of
+		(Function args def) -> f args def
+		(Dimension expr) -> getDepsExpr expr
+		(BasicDimension) -> []
+		(Builtin args def) -> f args def
+
+	where f args def = concatMap getDepsArg args ++ getDepsExpr def
+
+
+getDepsExpr :: Expr -> [Name]
+getDepsExpr (Bin _ expr1 expr2) = getDepsExpr expr1 ++ getDepsExpr expr2
+getDepsExpr (Uni _ expr) = getDepsExpr expr
+getDepsExpr (ArgRef _) = []
+getDepsExpr (Call n es) = n : concatMap getDepsExpr es
+getDepsExpr (Evaled (_, d)) = getDepsDims d
+
+getDepsArg :: Arg -> [Name]
+getDepsArg = getDepsDims . getArgType
+
+getDepsDims :: Dims -> [Name]
+getDepsDims (Dims d) = Map.keys d
+
+reverseDependencies :: Name -> Mon [Name]
+reverseDependencies n = do
+	state <- get
+	let 
+		all_ = Map.keys (getScope state)
+		filterF name_ = do
+			d <- dependencies name_
+			return $ n `elem` d
+
+	res <- liftM nub $ filterM filterF all_
+	if n `elem` all_
+		then return res
+		else fail ("no such thing: " ++ unName n)
+	
+
+getEntry :: Name -> Mon (Maybe StateEntry)
+getEntry s = do
+	state <- get
+	return $ Map.lookup s (getScope state)
+
+requireEntry :: Name -> Mon StateEntry
+requireEntry n = do
+	e <- getEntry n
+	case e of
+		Nothing -> throwError $ "No such object: " ++ pretty n
+		Just sth -> return sth
+
+requireFunction :: Name -> Mon (Args, Expr)
+requireFunction n = do
+	e <- requireEntry n
+	case e of
+		Function args expr -> return (args, expr)
+		Builtin args expr -> return (args, expr)
+		_ -> throwError $ pretty n ++ " is not a function"
+
+typeIsomorph :: StateEntry -> StateEntry -> Mon Bool
+typeIsomorph a b = case (a, b) of
+	(BasicDimension, BasicDimension) -> return True
+	(_, BasicDimension) -> return False
+	(BasicDimension, _) -> return False
+	(Dimension e1, Dimension e2) -> check1 e1 e2
+	(Dimension _, _) -> return False
+	(_, Dimension _) -> return False
+
+	(Function a1 e1, Function a2 e2) -> check2 e1 e2 a1 a2
+	(Builtin a1 e1, Builtin a2 e2) -> check2 e1 e2 a1 a2 -- FIXME rplc Builtin by Function Bool
+	(Builtin a1 e1, Function a2 e2) -> check2 e1 e2 a1 a2
+	(Function a1 e1, Builtin a2 e2) -> check2 e1 e2 a1 a2
+
+
+check1 :: Expr -> Expr -> Mon Bool
+check1 e1 e2 = checkReturnDims (e1, []) (e2, [])
+
+checkReturnDims :: (Expr, Args) -> (Expr, Args) -> Mon Bool
+checkReturnDims (e1, a1) (e2, a2) = do
+	(_, d1) <- doCall' a1 e1 (f a1)
+	(_, d2) <- doCall' a2 e2 (f a2)
+	(return d1 #==# return d2)
+
+	where 
+		f = map f'
+		f' :: Arg -> (R, Dims)
+		f' a = (undefined, getArgType a)
+
+--doCall' :: Args -> Expr -> [(R, Dims)] -> Mon (R, Dims)
+
+check2 :: Expr -> Expr -> Args -> Args -> Mon Bool
+check2 e1 e2 a1 a2 = (return a1 #==# return a2) #&&# checkReturnDims (e1, a1) (e2, a2)
+
+evalDimsPart :: Expr -> Mon Dims
+evalDimsPart e = do
+	res <- eval e
+	return $ snd res
+
+eval :: Expr -> Mon (R, Dims)
+eval (Call n args) = do
+	args' <- mapM eval args
+	doCall n args'
+
+eval (ArgRef (Arg _ i _)) = do
+	state <- get
+	getArgValues state #!!# i
+
+eval (Bin Add e1 e2) = eval e1 #+# eval e2
+eval (Bin Sub e1 e2) = eval e1 #-# eval e2
+eval (Bin Mul e1 e2) = eval e1 #*# eval e2
+eval (Bin Div e1 e2) = eval e1 #/# eval e2
+eval (Bin Exp e1 e2) = eval e1 #^# eval e2
+eval (Bin LogBase e1 e2) = eval e1 #~# eval e2
+
+eval (Uni Negate e) = negateM $ eval e
+eval (Uni Expot e) = expM $ eval e
+eval (Uni Log e) = logM $ eval e
+eval (Uni Sin e) = sinM $ eval e
+eval (Uni Cos e) = cosM $ eval e
+eval (Uni Tan e) = tanM $ eval e
+eval (Uni Asin e) = asinM $ eval e
+eval (Uni Acos e) = acosM $ eval e
+eval (Uni Atan e) = atanM $ eval e
+eval (Uni Sinh e) = sinhM $ eval e
+eval (Uni Cosh e) = coshM $ eval e
+eval (Uni Tanh e) = tanhM $ eval e
+eval (Uni Asinh e) = asinhM $ eval e
+eval (Uni Acosh e) = acoshM $ eval e
+eval (Uni Atanh e) = atanhM $ eval e
+
+eval (Evaled e) = return e
+
+(#!!#) :: Pretty a => [a] -> Int -> Mon a
+vals #!!# i = if (i < 0) || (length vals < i + 1)
+		then throwError $ "Index out of bounds: " ++ pretty vals ++ "!!" ++ pretty i
+		else return $ vals !! i
+
+
+doCall :: Name -> [(R, Dims)] -> Mon (R, Dims)
+doCall n args  = do
+	(sig, expr) <- requireFunction n
+	doCall' sig expr args
+
+doCall' :: Args -> Expr -> [(R, Dims)] -> Mon (R, Dims)
+doCall' sig expr args  = do
+
+	state <- get
+	let old = getArgValues state
+        modify (\x -> x {getArgValues = args})
+
+	when (length sig /= length args) (throwError "wrong number of arguments")
+	c <- check (zip (map snd args) sig)
+	when (not c) (throwError "wrong typed argument")
+
+	res <- eval expr
+	modify (\x -> x {getArgValues = old})
+	
+	return $ res
+
+check, check' :: [(Dims, Arg)] -> Mon Bool
+
+#ifdef DEBUG
+check l = trace (show l) (check' l)
+#else
+check = check'
+#endif
+
+check' [] = return True
+check' ((d', (Arg _ _ d)):as) = (return d' #==# return d) #&&# (check' as)
+
+
+instance EqM Arg (ErrorT String (SM.State State)) where
+	(#==#) a b = do
+		(Arg _ i1 t1) <- a
+		(Arg _ i2 t2) <- b
+		t <- (return t1) #==# (return t2)
+		return (t && i1 == i2)
+
+instance EqM [Arg] (ErrorT String (SM.State State)) where
+	(#==#) l1 l2 = let
+		nullM = liftM null
+		nNullM = liftM (not . null)
+		headM = liftM head
+		tailM = liftM tail in
+		caseM
+			[ (nullM l1 #&&# nullM l2, return True)
+			, (nNullM l1 #&&# nullM l2, return False)
+			, (nullM l1 #&&# nNullM l2, return False)]
+			((headM l1 #==# headM l2) #&&# (tailM l1 #==# tailM l2))
+
+caseM :: Monad m => [(m Bool, m a)] -> m a -> m a
+caseM [] base = base
+caseM ((cond, res):rest) base = ifM cond res (caseM rest base)
+
+ifM :: Monad m => (m Bool) -> m a -> m a -> m a
+ifM cond f s = do
+	cond' <- cond
+	if cond' then f else s
+
+convertBasic :: (R, Dims) -> Mon (R, Dims)
+convertBasic (r1, d1) = do
+	(r2, d2) <- compileDims d1
+	return (r1*r2, d2)
+
+
+convert :: (R, Dims) -> Dims -> Mon (R, Dims)
+convert (r, d) target = ifM
+	((return d) #==# (return target))
+	(do
+		(ra, _) <- compileDims d
+		(rb, _) <- compileDims target
+		return (r * ra / rb, target))
+	(throwError "Conversion to incompatible dimensions not possible.")
+
+compileDims :: Dims -> Mon (R, Dims)
+compileDims d = do
+	(r, d_) <- compileDims' d
+	return (r, Dims $ (Map.filter (/=0) . unDims) d_)
+
+compileDims' :: Dims -> Mon (R, Dims)
+compileDims' d = case dims2list d of
+	[] -> return (1, noDims)
+	[(n, i)] -> do
+		e <- requireEntry n
+		case e of 
+			BasicDimension -> return (1, Dims $ Map.singleton n i)
+			Dimension expr -> do
+				(r1, d1) <- eval (Bin Exp expr (Evaled (i, noDims)))
+				(r2, d2) <- compileDims d1
+				return (r1*r2, d2)
+			_ -> throwError $ pretty n ++ " is not a unit"
+	((n,i):ds) -> do
+		(r1, d1) <- compileDims (Dims $ Map.singleton n i)
+		(r2, d2) <- compileDims (Dims $ Map.fromList ds)
+		d_ <- (return d1) #*# (return d2)
+		return (r1*r2, d_)
+
+dims2list :: Dims -> [(Name, R)]
+dims2list d = Map.toList ((Map.filter (/=0) . unDims) d)
+
+canonicalizeDims :: Dims -> Mon Dims
+canonicalizeDims d = do
+	c <- compileDims d
+	return $ snd c
+
+instance EqM Dims (ErrorT String (SM.State State)) where
+	(#==#) d1 d2 = do
+		d1' <- d1
+		d2' <- d2
+		let 
+			c1 = canonicalizeDims d1'
+			c2 = canonicalizeDims d2'
+		res <- (liftM2 (\a b -> unDims a == unDims b)) c1 c2
+# ifdef DEBUG
+		d1'' <- c1
+		d2'' <- c2
+		return $ trace (show d1'' ++ " #==# " ++ show d2'' ++ " -> " ++ show res) res
+# else
+		return res
+# endif
+
+instance MulM Dims (ErrorT String (SM.State State)) where
+	(#*#) = std (+)
+
+instance DivM Dims (ErrorT String (SM.State State)) where
+	(#/#) e1 e2 = std (+) e1 (std' negate e2)
+
+dou :: R -> D
+dou x = (fromIntegral . numerator) x / (fromIntegral . denominator) x
+
+rat :: D -> R
+rat = toRational
+
+
+instance ExpM (R, Dims) (ErrorT String (SM.State State)) where
+	a #^# b = do
+		(ra, da) <- a
+		(rb, db) <- b
+		na <- nullD da
+		nb <- nullD db
+		let rn = rat $ dou ra ** dou rb
+		case (na, nb) of
+			(True, True) -> return (rn, noDims)
+			(False, True) -> if_ (denominator rb == 1)
+				(do d <- da *** rb; return (rn, d))
+				(do
+ 					(r, d) <- convertBasic (ra, da)
+					d'  <- d *** rb
+					return (rat $ dou r ** dou rb, d'))
+			(_, False) -> throwError $ "Operation requires a number without unit: " ++ pretty (Evaled (ra, da)) ++ " #^# " ++ pretty (Evaled (rb, db))
+
+toI :: Integral a => Ratio a -> Mon a
+toI x = let a = numerator x; b = denominator x in
+	if_ (b == 1) (return a) (throwError "Integer required.")
+
+instance LogBaseM (R, Dims) (ErrorT String (SM.State State)) where 
+	a #~# b = do
+		(ra, da) <- a
+		(rb, db) <- b
+		ifM (nullD da #&&# nullD db) (return $ (rat $ logBase (dou ra) (dou rb), noDims))
+			(do
+				ia <- toI ra
+				ib <- toI rb
+				case logBaseInt ia ib of
+					Nothing -> throwError "Integer exponent required for logbase on values with dimensions."
+					Just re -> do
+						ifM (da *** (re%1) #==# return db)
+							(return ((re%1), noDims))
+							(throwError "Dimensions are in other logbase relation than the numbers"))
+{-
+(***) :: Dims -> R -> Mon Dims
+(***) (Dims d) r = do
+	let res = Map.map (\x -> x * r) d
+	if Map.null $ Map.filter (\x -> denominator x /= 1) res
+		then return $ Dims $ Map.map (fromIntegral . numerator) res
+		else throwError $ "Operation requires a number without unit: " ++ pretty (Dims d) ++ " *** " ++ pretty r
+-}
+
+(***) :: Dims -> R -> Mon Dims
+(***) (Dims d) r = return (Dims $ Map.map (\x -> x * r) d)
+
+
+std :: Monad m => (R -> R -> R) -> (m Dims -> m Dims -> m Dims)
+std f = liftM2 (\ a b -> Dims $ Map.unionWith f (Map.filter (/=0) $ unDims a) (Map.filter (/=0) $ unDims b))
+
+std' :: Monad m => (R -> R) -> (m Dims -> m Dims)
+std' f = liftM (\ a -> Dims $ Map.map f (Map.filter (/=0) $ unDims a))
+
+nullD :: Dims -> Mon Bool
+nullD d = return d #==# return noDims
+
+run :: State -> Command -> (Either String Result, State)
+run state command = (runState $ runErrorT (process command)) state
+
+uniInstance :: (Double -> Double) -> Mon (R, Dims) -> Mon (R, Dims)
+uniInstance fr a = do
+	(r, d) <- a
+	return (rat . fr . dou $ r, d)
+
+minDims :: Dims -> Mon Dims
+minDims d = do
+	state <- get
+	let
+		isDims = (\x -> case x of BasicDimension -> True; (Dimension _) -> True; _ -> False)
+		neg a = justDo (return noDims #/# return a)
+		allDims = map (\x -> Dims $ Map.singleton x 1) $ Map.keys $ Map.filter isDims $ getScope state
+
+		test :: Dims -> Mon Bool
+		test d' = return d' #==# return d
+
+		merge :: [Dims] -> Dims
+		merge = foldl (\a b -> justDo (return a #*# return b)) noDims
+
+		combineUpTo :: Int -> [a] -> [[a]]
+		combineUpTo i l = concatMap (\i' -> combination i' l) [1..i]
+
+		unique :: [Dims] -> [(Dims, [Dims])]
+		unique = eqClassesWith (\a b -> justDo (return a #==# return b))
+		
+		dims = map fst $ unique allDims
+
+		justDo f = case fst $ (runState $ runErrorT f) state of Left e -> error e; Right b -> b
+
+		dimsList = map merge $ combineUpTo 2 $ (map neg dims ++ dims)
+
+	liftM (headWithDefault d) $ filterM test $ dimsList
+
+instance AddM (R, Dims) (ErrorT String (SM.State State)) where 
+	( #+# ) = linear (+)
+
+linear :: (R -> R -> R) -> Mon (R, Dims) -> Mon (R, Dims) -> Mon (R, Dims)
+
+linear f a b = do
+	(ra, da) <- a
+	b'@(_, db) <- b
+	(rb, _) <- convert b' da
+
+	ifM (return da #==# return db)
+		(return (f ra rb, da))
+		(throwError "Incompatible dimensions cannot be added.")
+
+muldiv :: (R -> R -> R) -> (Mon Dims -> Mon Dims -> Mon Dims) 
+	-> Mon (R, Dims) -> Mon (R, Dims) -> Mon (R, Dims)
+muldiv fr fd a b = do
+	(ra, da) <- a
+	(rb, db) <- b
+	d <- fd (return da) (return db)
+	return (fr ra rb, d)
+
+instance SubM (R, Dims) (ErrorT String (SM.State State)) where 
+	( #-# ) = linear (-)
+
+instance MulM (R, Dims) (ErrorT String (SM.State State)) where 
+	( #*# ) = muldiv (*) ( #*# )
+
+instance DivM (R, Dims) (ErrorT String (SM.State State)) where 
+	( #/# ) = muldiv (/) ( #/# )
+
+instance NegateM (R, Dims) (ErrorT String (SM.State State)) where 
+	negateM = liftM (\ (r,d) -> (negate r, d))
+
+instance ExpotM (R, Dims) (ErrorT String (SM.State State)) where 
+	expM = uniInstance exp
+
+instance LogM (R, Dims) (ErrorT String (SM.State State)) where 
+	logM = uniInstance log
+
+instance SinM (R, Dims) (ErrorT String (SM.State State)) where 
+	sinM = uniInstance sin
+
+instance CosM (R, Dims) (ErrorT String (SM.State State)) where 
+	cosM = uniInstance cos
+
+instance TanM (R, Dims) (ErrorT String (SM.State State)) where 
+	tanM = uniInstance tan
+
+instance AsinM (R, Dims) (ErrorT String (SM.State State)) where 
+	asinM = uniInstance asin
+
+instance AcosM (R, Dims) (ErrorT String (SM.State State)) where 
+	acosM = uniInstance acos
+
+instance AtanM (R, Dims) (ErrorT String (SM.State State)) where 
+	atanM = uniInstance atan
+
+instance SinhM (R, Dims) (ErrorT String (SM.State State)) where 
+	sinhM = uniInstance sinh
+
+instance CoshM (R, Dims) (ErrorT String (SM.State State)) where 
+	coshM = uniInstance cosh
+
+instance TanhM (R, Dims) (ErrorT String (SM.State State)) where 
+	tanhM = uniInstance tanh
+
+instance AsinhM (R, Dims) (ErrorT String (SM.State State)) where 
+	asinhM = uniInstance asinh
+
+instance AcoshM (R, Dims) (ErrorT String (SM.State State)) where 
+	acoshM = uniInstance acosh
+
+instance AtanhM (R, Dims) (ErrorT String (SM.State State)) where 
+	atanhM = uniInstance atanh
diff --git a/src/Language/CalDims/Expr.hs b/src/Language/CalDims/Expr.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Expr.hs
@@ -0,0 +1,96 @@
+{-# LANGUAGE FlexibleInstances #-}
+
+module Language.CalDims.Expr 
+	( Expr (..)
+	, BinOp (..)
+	, UniOp (..))
+	
+where
+
+import Language.CalDims.Types
+
+instance Pretty BinOp where
+        pretty Add = " + "
+        pretty Sub = " - "
+        pretty Mul = " * "
+        pretty Div = " / "
+        pretty Exp = " ^ "
+	pretty LogBase = " ~ "
+
+instance Pretty (R, Dims) where
+        pretty = pretty . Evaled
+
+instance Pretty Expr where
+
+	pretty (Evaled (r, d)) = let d' = pretty d in
+		pretty r ++ (if null d' then "" else " " ++ d')
+
+        pretty expr@(Bin kind a b) = s1 ++ pretty kind ++ s2
+
+		where
+			p = priority expr
+
+			-- exp is right-associative
+			s1 = if kind == Exp then prettyP2 p a else prettyP1 p a
+
+			s2 = case (kind == Exp, isAssoc kind) of
+				(True, _) -> prettyP1 p b
+				(_, True) -> prettyP1 p b
+				_ -> prettyP2 p b
+
+        pretty (Uni Negate a) = "-" ++ prettyP1 P_Negate a
+
+        pretty (Uni Expot a) = oneF "exp" a
+        pretty (Uni Log a) = oneF "log" a
+        pretty (Uni Sin a) = oneF "sin" a
+        pretty (Uni Cos a) = oneF "cos" a
+        pretty (Uni Tan a) = oneF "tan" a
+        pretty (Uni Asin a) = oneF "asin" a
+        pretty (Uni Acos a) = oneF "acos" a
+        pretty (Uni Atan a) = oneF "atan" a
+        pretty (Uni Sinh a) = oneF "sinh" a
+        pretty (Uni Cosh a) = oneF "cosh" a
+        pretty (Uni Tanh a) = oneF "tanh" a
+        pretty (Uni Asinh a) = oneF "asinh" a
+        pretty (Uni Acosh a) = oneF "acosh" a
+        pretty (Uni Atanh a) = oneF "atanh" a
+
+        pretty (ArgRef (Arg name _ _)) = name
+        pretty (Call name []) = pretty name
+        pretty (Call name argList) = pretty name ++ " (" ++ (pretty $ head argList) ++ (unwords $ map (\x -> ", " ++ pretty x) $ tail argList) ++ ")"
+
+
+
+-- Functions
+
+priority :: Expr -> Priority
+priority (Bin Add _ _) = P_Add
+priority (Bin Sub _ _) = P_Add
+priority (Bin Mul _ _) = P_Mul
+priority (Bin Div _ _) = P_Mul
+priority (Bin Exp _ _) = P_Exp
+priority (Uni Negate _) = P_Negate
+priority (Evaled _) = P_Mul
+priority _ = P_Elementary
+
+isAssoc :: BinOp -> Bool
+isAssoc Add = True
+isAssoc Mul = True
+isAssoc _ = False
+
+prettyB :: Expr -> String
+prettyB a@(Evaled _) = pretty a
+prettyB a@(Call _ _) = pretty a
+prettyB a@(ArgRef _) = pretty a
+prettyB a@(Bin _ _ _) = "(" ++ pretty a ++ ")"
+prettyB a@(Uni _ _) = "(" ++ pretty a ++ ")"
+
+prettyP1, prettyP2 :: Priority -> Expr -> String
+prettyP1 = prettyP' (>)
+prettyP2 = prettyP' (>=)
+
+prettyP' :: (Priority -> Priority -> Bool) -> Priority -> Expr -> String
+prettyP' f p e = if p `f` priority e then prettyB e else pretty e
+
+oneF :: String -> Expr -> String
+oneF fn e = fn ++ " (" ++ pretty e ++ ")"
diff --git a/src/Language/CalDims/Expression.hs b/src/Language/CalDims/Expression.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Expression.hs
@@ -0,0 +1,293 @@
+{-# LANGUAGE CPP #-}
+module Language.CalDims.Expression 
+	( parseExpr
+	, parseName
+	, parseExistingName
+	, parseBindE
+	, parseEinh
+	, parseBind
+	, brackets
+	, parseNonRecursiveExpr
+	, parseColon
+	, parseComma
+	, flush) where
+
+import Text.ParserCombinators.Parsec
+import Text.ParserCombinators.Parsec.Prim
+import Text.ParserCombinators.Parsec.Expr
+import Ratio ((%))
+import Control.Monad.Error
+import Control.Monad.State
+import Control.Monad
+import qualified Data.Map as Map
+
+#ifdef DEBUG
+import Debug.Trace
+#endif
+
+import Language.CalDims.Expr ()
+import Language.CalDims.Types
+import Language.CalDims.Action
+import Language.CalDims.State as State
+import Language.CalDims.Helpers
+
+requireEntry :: Name -> MyParser StateEntry
+requireEntry n = do
+	state <- getState
+        case Map.lookup n (getScope state) of
+                Nothing -> fail $ "No such object: " ++ pretty n
+                Just sth -> return sth
+
+hnn, hasNotName :: Expr -> Name -> MyParser Bool
+#ifdef DEBUG
+hasNotName e n = do
+	res <- hnn e n
+	return $ trace (show e ++ " `hasNotName` " ++ show n ++ " -> " ++ show res) res
+#else
+hasNotName = hnn
+#endif
+
+(Bin _ e1 e2) `hnn` n = (e1 `hasNotName` n) #&&# (e2 `hasNotName` n)
+(Uni _ e) `hnn` n = e `hasNotName` n
+(ArgRef _) `hnn` _ = return True
+(Call fn args) `hnn` n = do
+	e_ <- requireEntry fn
+	case e_ of
+		Function _ e -> (return (fn /= n)) #&&# (liftM and) (sequence  (map (`hasNotName` n) args)) #&&# (e `hasNotName` n)
+		_ -> return True -- call to builtin
+
+(Evaled (_, Dims m)) `hnn` n = do
+        state <- getState
+        let exprs = Map.elems $ Map.mapMaybeWithKey (\k v -> if_ 
+		(k `Map.member` m) 
+		(case v of Dimension e -> Just e; _ -> Nothing) 
+		Nothing) (getScope state)
+        (return $ not (n `Map.member` m)) #&&# (liftM and) (sequence (map (`hasNotName` n) exprs))
+
+flush :: GenParser Char State.State (IO(), State.State)
+flush = do
+        many $ noneOf []
+        eof
+        s <- getState
+        return (return (), s)
+
+binary :: String -> (Expr -> Expr -> Expr) -> Assoc -> Operator Char State.State Expr
+binary s f assoc = Infix (do
+	string s
+	spaces
+	return f) assoc
+
+parseExpr :: MyParser Expr
+parseExpr  = do
+	buildExpressionParser table factor
+        <?> "expression"
+
+parseNonRecursiveExpr :: Name -> MyParser Expr
+parseNonRecursiveExpr n = do
+	e <- parseExpr
+	t <- e `hasNotName` n
+	case t of
+		True -> return e
+		False -> fail "No recursion supported."
+
+table :: OperatorTable Char State.State Expr
+table  = [
+	  [Prefix (do
+		parseMinus
+		return $ Uni Negate)],
+          [binary "^" (Bin Exp) AssocRight],
+          [Postfix (do 
+		d <- parseEinh
+		return $ mulMerge (Evaled (1, d)))],
+          [binary "~" (Bin LogBase) AssocLeft],
+	  [binary "*" (Bin Mul) AssocLeft, binary "/" (Bin Div) AssocLeft],
+          [binary "+" (Bin Add) AssocLeft, binary "-" (Bin Sub) AssocLeft]
+         ]
+     
+
+mulMerge :: Expr -> Expr -> Expr
+mulMerge (Evaled (ra, da)) (Evaled (rb, db)) = Evaled (ra*rb, f da db) where 
+	f a b = Dims $ Map.unionWith (+) (Map.filter (/=0) $ unDims a) (Map.filter (/=0) $ unDims b)
+mulMerge e1 e2 = Bin Mul e1 e2
+
+parseArgRef, factor, call :: MyParser Expr
+
+factor = brackets parseExpr <|> number <|> try parseArgRef <|> call
+
+call = (do
+        (n, e) <- parseExistingName
+        args <- option [] (brackets (parseExpr `sepBy` parseComma))
+	case e of
+		(Function _ _) -> test n args
+		(Builtin _ _) -> test n args
+		_ -> fail $ pretty n ++ " is not a function"
+	) <?> "function application"
+	where
+		test :: Name -> [Expr] -> MyParser Expr
+		test n args = do
+			state <- getState
+			case (runState $ runErrorT (do
+					args' <- mapM eval args
+					doCall n args')) state of
+				(Left e, _) -> fail e
+				(Right _, _) -> return (Call n args) -- doCall should not change the state
+
+
+parseArgRef = (do
+        n' <- parseName
+	let n = unName n'
+	state <- getState
+	case constrArgRef 0 n (getArgs state) of
+		Left s -> fail s
+		Right e -> return e
+	) <?> "argument reference"
+
+	where
+		constrArgRef :: Int -> String -> Args -> Either String Expr
+		constrArgRef _ s [] = Left $ "no such argument in definition list: " ++ pretty s
+		constrArgRef i s (a:as)
+			| getArgName a == s = Right $ ArgRef (Arg s i (getArgType a))
+			| otherwise = constrArgRef (i+1) s as
+
+
+parseEinh :: MyParser Dims
+parseEinh = do
+	res <- many1 eh0
+	state <- getState
+	case (runState $ runErrorT (mergeDims res)) state of
+		(Left e, _) -> fail e
+		(Right dims, _) -> return dims -- mergeDims is not supposed to change the state
+
+mergeDims :: [(Mon Dims -> Mon Dims)] -> Mon Dims
+mergeDims [] = return noDims
+mergeDims [a] = a (return noDims)
+mergeDims (a:as) = a (mergeDims as)
+
+eh0 :: MyParser (Mon Dims -> Mon Dims)
+eh0 = try (do
+	op <- option (#*#) (do
+		spaces
+		char '/'
+		return (#/#))
+	spaces
+	r <- eh1
+	return ((flip op) (return r)))
+
+
+eh1 :: MyParser Dims
+eh1  = 	try (do spaces; char '('; spaces; r <- parseEinh ; spaces; char ')'; return r;) <|> (do
+        n <- eh2
+        option (Dims $ Map.singleton n 1) (do
+		spaces
+                char '^'
+		spaces
+                i <- fractOrInt
+		spaces
+                return $ Dims $ Map.singleton n i))
+
+eh2 :: MyParser Name
+eh2  = try (do
+      	(name, entry) <- parseExistingName
+	case entry of
+		BasicDimension -> return name
+		Dimension _ -> return name
+		_ -> fail (pretty name ++ " is not a unit")
+	) <?> "unit name"
+
+parseName :: MyParser Name
+parseName = do
+        r1 <- letter
+        r2 <- many (oneOf "_'" <|> digit <|> letter)
+        spaces
+        return $ Name (r1:r2)
+
+
+parseExistingName :: MyParser (Name, StateEntry)
+parseExistingName = do
+        n <- parseName
+	e <- requireEntry n
+	return $! (n, e)
+
+int :: MyParser Integer
+int = do
+	o <- option ' ' $ char '-'
+	spaces
+	n <- many1 digit
+	spaces
+	return $ ((read $ o:n)::Integer)
+
+number :: MyParser Expr
+number = do
+	n <- (try fract) <|> real
+	spaces
+	return $ Evaled (n, noDims)
+
+
+
+fractOrInt :: MyParser R
+fractOrInt = (try fract) <|> intF
+
+intF :: MyParser R
+intF = do
+	spaces
+	r <- int
+	spaces
+	return (r % 1)
+
+fract :: MyParser R
+fract = do
+	spaces
+	r1 <- many1 digit
+	spaces
+	char '%'
+	spaces
+	r2 <- many1 digit
+	spaces
+	return $ ((read r1)::Integer)%((read r2)::Integer)
+
+real :: MyParser R
+real  = do
+	r1 <- many1 digit
+	res <- option (fromInteger ((read r1)::Integer)) (do
+		char '.'
+		r2 <- many1 digit
+		spaces
+		let
+			rr1 = ((read r1)::Integer)
+			rr2 = ((read r2)::Integer) -- FIXME it may be more efficient to textually append length r2 zeros here.
+			l = 10^length r2
+		return $ (rr1 * l + rr2) % l)
+
+	res' <- option res (try (do
+		spaces
+		char 'e'
+		spaces
+		f <- option id (do {char '-'; return negate})
+		spaces
+		exp_ <- many1 digit
+		spaces
+		return (res * (10 ^^ f (read exp_ :: Integer)))))
+
+	return res'
+	<?> "real"
+
+parseMinus, parseColon, parseBind, parseBindE, parseLB, parseRB, parseComma :: MyParser String
+parseMinus  = addSpace (string "-")
+parseColon  = addSpace (string ":")
+parseBind   = addSpace (string "=")
+parseBindE  = addSpace (string ":=")
+parseLB     = addSpace (string "(")
+parseRB     = addSpace (string ")")
+parseComma  = addSpace (string ",")
+
+brackets,  addSpace :: MyParser a -> MyParser a
+brackets p = try (do
+        parseLB
+        r <- p
+        parseRB
+        return r)
+
+addSpace a = do
+	r <- a
+	spaces
+	return r
diff --git a/src/Language/CalDims/Helpers.hs b/src/Language/CalDims/Helpers.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Helpers.hs
@@ -0,0 +1,80 @@
+
+module Language.CalDims.Helpers 
+	( F
+	, headWithDefault
+	, again
+	, third
+	, unlines'
+	, logBaseInt
+	, (#&&#)
+	, combination
+	, permutation
+	, if_ -- functional if
+	, ErrorAndState
+	, eqClassesWith
+	) where
+
+import Control.Monad.Error
+import Control.Monad.State
+
+type ErrorAndState e s a = ErrorT e (State s) a
+type F = Double
+
+
+unlines' :: [String] -> String
+unlines' [] = ""
+unlines' [a] = a
+unlines' (a:as) = a ++ "\n" ++ unlines' as
+
+logBaseInt :: Integral a => a -> a -> Maybe a
+logBaseInt a b = if a ^ res == b then Just res else Nothing
+	where
+		res = round (logBase (fromIntegral a) (fromIntegral b) :: Double)
+
+again :: Monad m => (a -> m b) -> [a] -> m ()
+again _ [] = return ()
+again f (x:xs) = f x >> again f xs
+
+headWithDefault ::  a -> [a] -> a
+headWithDefault a [] = a
+headWithDefault _ (a:_) = a
+
+(#&&#) :: Monad m => m Bool -> m Bool -> m Bool
+(#&&#) = liftM2 (&&)
+
+third :: (a, b, c) -> c
+third (_, _, c) = c
+
+--tc :: Eq a => (a -> [a]) -> a -> [a]
+--tc f start = start : concatMap (tc f) (filter (/= start) $ f start)
+
+if_ :: Bool -> a -> a -> a
+if_ True a _ = a
+if_ False _ b = b
+
+eqClassesWith :: (a -> a -> Bool) -> [a] -> [(a,[a])]
+eqClassesWith f l = foldl (ff f) [] l
+
+ff :: (a -> a -> Bool) -> [(a, [a])] -> a -> [(a, [a])]
+ff _ [] a = [(a, [])]
+ff f ((r,rs):on) a = if f r a then ((r,(a:rs)):on) else (r,rs):(ff f on a)
+
+-- combination i l lists all combinations (without repetitions) of set l of order i
+-- example:
+-- ["abc","abd","acd","bcd"]
+
+combination :: Int -> [a] -> [[a]]
+combination i l
+	| i > length l = error "i > len l"
+	| i == 1 = map (\x -> [x]) l
+	| null l = []
+	| i == length l = [l]
+	| otherwise = let (a:as) = l in
+		zipWith (:) (repeat a) (combination (i - 1) as) ++ combination i as
+
+
+permutation :: Int -> [a] -> [[a]]
+permutation i l
+	| i < 1 = error "i > len l"
+	| i == 1 = map (\x -> [x]) l
+	| otherwise = [ x:y | x <- l, y <- (permutation (i - 1) l)]
diff --git a/src/Language/CalDims/Misc.hs b/src/Language/CalDims/Misc.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Misc.hs
@@ -0,0 +1,176 @@
+module Language.CalDims.Misc (parseLine) where
+
+import Text.ParserCombinators.Parsec
+import qualified Data.List as List
+import Control.Monad
+
+import Language.CalDims.Expression
+import Language.CalDims.Expr ()
+import Language.CalDims.Action
+import Language.CalDims.Types
+
+
+eof' :: MyParser ()
+eof' = do
+	spaces
+	eof
+
+parseConversion :: MyParser Conversion
+parseConversion = do
+	spaces
+	char '|'
+	spaces
+	c <- try (pr parseEinh Explicit) <|> try (pr parseExpr InTermsOf) <|>
+		(char '-' >> return Basic) <|>
+		(char '*' >> return Keep) <|>
+		(char '?' >> return Minimal)
+	spaces
+	return c
+	where pr f rc = f >>= return . rc
+
+parseFilename :: MyParser String
+parseFilename = many1 (oneOf (['a'..'z'] ++ ['A'..'Z'] ++ ['0'..'9'] ++ ['_', '.', '-']))
+
+parseShort :: String -> MyParser String
+parseShort s = do
+	res <- string $ "\\" ++ s
+	(char ' ' >> return ()) <|> eof
+	spaces
+	return res
+
+parseGetState, parseWriteState, parseDebugName, parseDebugExpr, parseDebugDependencies, parseEval,  parseHelp, parseRemove, parseRemoveCascade, parseEcho, parseAddUnit, parseAddBasicUnit, parseAddFunction :: MyParser Command
+
+parseComment, parseEmpty :: MyParser ()
+
+parseGetState = do
+	parseShort "s"
+	eof'
+	return GetState
+
+parseWriteState = do
+	parseShort "s"
+	name <- parseFilename
+	eof'
+	return $ WriteState name
+
+parseDebugExpr = do
+	try (parseShort "de") <|> parseShort "d"
+	e <- parseExpr
+	eof'
+	return $ DebugExpr e
+
+parseDebugName = do
+	parseShort "dn"
+	n <- parseName
+	eof'
+	return $ DebugName n
+
+parseDebugDependencies = do
+	parseShort "dp"
+	n <- parseName
+	eof'
+	return $ DebugDependencies n	
+
+parseEval = do
+	e <- parseExpr
+	conversion <- option Keep parseConversion
+	eof'
+	return $ Eval e conversion
+
+parseComment = do
+	spaces
+	char '#'
+	flush
+	return ()
+
+parseEmpty = do
+	spaces
+	eof'
+	return ()
+
+parseHelp = do
+	parseShort "?"
+	eof'
+	return Help
+
+parseRemove = do
+	parseShort "r"
+	name <- parseName
+	eof'
+	return $ Remove name
+
+parseRemoveCascade = do
+	parseShort "rc"
+	name <- parseName
+	eof'
+	return $ RemoveCascade name
+
+parseEcho = do
+	parseShort "p"
+	s <- many1 anyChar
+	eof'
+	return $ Echo s
+
+parseAddBasicUnit = do
+	parseShort "u"
+	name <- parseName
+	eof'
+	return $ AddBasicUnit name
+
+parseAddUnit = do
+	fn <- parseName
+	parseBindE
+	expr <- parseNonRecursiveExpr fn
+	return $ AddUnit fn expr
+
+parseAddFunction = do
+	oState <- getState
+	fn <- parseName
+	args' <- option [] (brackets (sepBy (do
+		n <- parseName
+		e <- option noDims (do
+			parseColon
+			parseEinh)
+		return $ Arg (unName n) 0 e) parseComma))
+	let args = zipWith (\ (Arg s _ d) n -> Arg s n d) args' [0..]
+	parseBind
+	updateState (\x -> x {getArgs = args, getArgValues = map (\ (Arg _ _ d) -> (undefined, d)) args})
+	expr <- parseNonRecursiveExpr fn
+	when (getArgRefs expr /= (List.nub . List.sort $ args)) (fail "one/some of the parameters are not used in the expression")
+	updateState (\_ -> oState)
+	return $ AddFunction fn  args  expr
+
+getArgRefs', getArgRefs :: Expr -> [Arg]
+
+getArgRefs = List.nub . List.sort . getArgRefs'
+
+getArgRefs' (Bin _ e1 e2) = getArgRefs e1 ++ getArgRefs e2
+getArgRefs' (Uni _ e) = getArgRefs e
+getArgRefs' (ArgRef r) = [r]
+getArgRefs' (Call _ es) = foldl (++) [] (map getArgRefs es)
+getArgRefs' (Evaled _) = []
+
+parseLine :: MyParser (Maybe Command)
+parseLine  = do
+
+	let all_ =
+		map try 
+		[ parseGetState
+		, parseWriteState
+		, parseDebugName
+		, parseDebugExpr
+		, parseDebugDependencies
+		, parseHelp
+		, parseRemove
+		, parseRemoveCascade
+		, parseEcho
+		, parseAddBasicUnit
+		, parseEval
+		, parseAddUnit
+		, parseAddFunction
+
+		]
+	spaces
+	command <- (do parseComment <|> parseEmpty; return Nothing) <|> (do res <- foldl1 (<|>) all_; return $ Just res)
+	eof'
+	return command
diff --git a/src/Language/CalDims/Program.hs b/src/Language/CalDims/Program.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Program.hs
@@ -0,0 +1,141 @@
+module Language.CalDims.Program (getUserState, loop, OutputMode (..), omRun, prompt, defMain) where
+
+import Text.ParserCombinators.Parsec
+import qualified Data.List as List
+import System.IO
+import qualified System.Directory as Dir
+import System.Environment as E
+import System.Console.Readline
+import Control.Monad
+import System.Console.GetOpt
+
+import Language.CalDims.Action
+import Language.CalDims.State as S
+import Language.CalDims.Types
+import qualified Language.CalDims.Texts as Texts
+import Language.CalDims.Helpers
+import Language.CalDims.Misc
+import Language.CalDims.Texts
+
+prompt :: String
+prompt = "> "
+
+getLine' :: Handle -> IO (Maybe String)
+getLine' h = do
+	i <- hIsTerminalDevice h
+	if i then readline prompt else catch (do {l <- hGetLine h; return $ Just l}) (\_ -> return Nothing)
+
+data OutputMode = OutputMode
+	{ ppResult :: Bool -- pretty print result
+	, ppCommand :: Bool -- pretty print command
+	, sResult :: Bool -- show result
+	, sCommand :: Bool -- show command
+	, echo :: Bool -- echo input
+	, pErrors :: Bool -- print errors
+	, tolerant :: Bool -- go on after error
+	} deriving (Read, Show)
+
+omPrelude, omRun :: OutputMode
+omPrelude = OutputMode False False False False False True False
+omRun = OutputMode True False False False False True True
+
+loop :: OutputMode -> Handle -> S.State -> IO S.State
+loop om h state = do
+	line' <- getLine' h
+	case line' of
+		Nothing -> return state -- EOF
+		Just line -> do
+			addHistory line
+			when (echo om) (putStrLn $ prompt ++ line)
+			case runParser parseLine state "" line of
+				Left e -> do
+					when (pErrors om) (putStrLn . last . lines . show $ e)
+					if (tolerant om)
+						then loop om h state
+						else error (show e)
+
+				 -- no error, but no command either (empty line or comment)
+				Right Nothing -> loop om h state
+
+				Right (Just command) -> do
+					when (sCommand om) (print command)
+					when (ppCommand om) (putStrLn $ pretty command)
+
+					case run state command of
+						(Left e, _) -> do
+							when (pErrors om) (putStrLn e)
+							if tolerant om
+								then loop om  h state
+								else error e
+						(Right res, newState) -> do
+							when (sResult om) (print res)
+							when (ppResult om) (putStrLn $ pretty res)
+							loop om h newState
+
+
+
+
+getUserState :: Maybe String -> IO S.State
+getUserState mfn = do
+
+        sdir <- Dir.getCurrentDirectory
+
+        filename <- case mfn of
+                Nothing -> (do
+                        let
+                                file = "prelude.cal"
+
+                        dir <- Dir.getAppUserDataDirectory "CalDims"
+                        Dir.createDirectoryIfMissing True dir
+                        Dir.setCurrentDirectory dir
+                        exists <- Dir.doesFileExist file
+
+                        unless exists (do
+                                handle <- openFile file WriteMode
+                                hPutStr handle Texts.preludeText
+                                hClose handle)
+                        return file)
+                Just fns -> return fns
+
+        handle <- openFile filename ReadMode
+        Dir.setCurrentDirectory sdir
+        loop omPrelude handle start
+
+data CliArg = DoEcho | Blank | DisplayHelp deriving Eq
+
+exit :: [String] -> IO a
+exit s = error (unlines s)
+
+defMain :: IO()
+defMain = do
+	interactive <- hIsTerminalDevice stdin
+	when interactive (do
+		putStrLn Texts.welcomeText 
+		hFlush stdout)
+
+	args <- E.getArgs
+	
+	let 
+		descr = 
+			[ Option "e" ["echo"] (NoArg DoEcho) "echo input line"
+			, Option "b" ["blank"] (NoArg Blank) "load no configuration file"
+			, Option "h" ["help"] (NoArg DisplayHelp) "display help" ]
+		(opts, fns, errs) = getOpt RequireOrder descr args
+
+	when (not $ null errs) (exit (errs ++ [usageInfo "caldims [OPTIONS] FILE" descr]))
+
+	let omRun_ = if_
+		(DoEcho `elem` opts)
+		(omRun {echo = True})
+		omRun
+
+	if DisplayHelp `elem` opts then print helpText else (do
+
+		s <- case (Blank `elem` opts, fns) of
+			(False, []) 		-> getUserState Nothing
+			(False, [filename]) 	-> getUserState (Just filename)
+			(True, []) 		-> return start
+			(_, (_:_:_))		-> exit ["too many FILE arguments"]
+			(True, (_:_))		-> exit ["blank start requested, but filename given."]
+		loop omRun_ stdin s
+		return ())
diff --git a/src/Language/CalDims/State.hs b/src/Language/CalDims/State.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/State.hs
@@ -0,0 +1,81 @@
+{-# OPTIONS -fglasgow-exts #-}
+
+module Language.CalDims.State 
+	( MyParser
+	, Arg (..)
+	, Args
+	, Scope
+	, State (..)
+	, StateEntry (..)
+	, isBasicUnit
+	, isUnit
+	, isDerivedUnit
+	, isFunction
+	, isBuiltin
+	, lu
+	, start) where
+
+import qualified Data.Map as Map
+import qualified Data.List as List
+import Data.Maybe
+
+import Language.CalDims.Types
+import Language.CalDims.Expr ()
+
+
+start :: State
+start = State 
+	{ getScope = Map.fromList [ (Name "pi", Builtin [] $ Evaled (toRational ((pi)::Double), noDims))
+                                  , (Name "e", Builtin [] $ Evaled (toRational ((exp 1):: Double), noDims))
+                                  , (Name "exp", bUni Expot noDims)
+                                  , (Name "log", bUni Log noDims)
+                                  , (Name "cos", bUni Cos noDims)
+                                  , (Name "tan", bUni Tan noDims)
+                                  , (Name "asin", bUni Asin noDims)
+                                  , (Name "acos", bUni Acos noDims)
+                                  , (Name "atan", bUni Atan noDims)
+                                  , (Name "sinh", bUni Sinh noDims)
+                                  , (Name "cosh", bUni Cosh noDims)
+                                  , (Name "tanh", bUni Tanh noDims)
+                                  , (Name "asinh", bUni Asinh noDims)
+                                  , (Name "acosh", bUni Acosh noDims)
+                                  , (Name "atanh", bUni Atanh noDims)
+                                  , (Name "sin", bUni Sin noDims)]
+	, getArgs = []
+	, getArgValues = []}
+
+bUni :: UniOp -> Dims -> StateEntry
+bUni o d = let arg = Arg "x" 0 d in Builtin [arg] $ Uni o (ArgRef arg)
+
+instance Pretty (Name, StateEntry) where
+	pretty (name, Function args expr) = pretty name ++ prettyArgs args ++ " = " ++ pretty expr
+	pretty (name, Builtin args _) = pretty name ++ prettyArgs args ++ " = [[builtin]]"
+	pretty (name, Dimension expr) = pretty name ++ " := " ++ pretty expr
+	pretty (name, BasicDimension) = "\\u " ++ pretty name
+
+prettyArgs :: Args -> String
+prettyArgs [] = ""
+prettyArgs args = " (" ++ foldl1 (\a b -> a ++ ", " ++ b) (map (\ (Arg n _ d) -> n ++ " : " ++ pretty d) args) ++ ")"
+
+isBasicUnit, isUnit, isDerivedUnit, isFunction, isBuiltin :: State -> Name -> Bool
+isBasicUnit state name
+	| Just BasicDimension <- lu name state = True
+        | otherwise = False
+
+isFunction state name
+	| Just (Function _ _) <- lu name state = True
+        | otherwise = False
+
+isBuiltin state name
+	| Just (Builtin _ _) <- lu name state = True
+        | otherwise = False
+
+isDerivedUnit state name
+        | Just (Dimension _) <- lu name state = True
+        | otherwise = False
+
+isUnit state name = isDerivedUnit state name || isBasicUnit state name
+
+lu :: Name -> State -> Maybe StateEntry
+lu name state = Map.lookup name (getScope state)
+
diff --git a/src/Language/CalDims/Texts.hs b/src/Language/CalDims/Texts.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Texts.hs
@@ -0,0 +1,204 @@
+module Language.CalDims.Texts where
+
+import qualified Data.Version as Version
+
+-- Types
+
+data HelpTree = Section String [HelpTree] | Para String
+
+-- Classes
+
+-- Instances
+
+instance Show HelpTree where
+	show = unlines . show' 0
+		where
+
+		show' :: Int -> HelpTree -> [String]
+		show' level ht = case ht of 
+			(Section s list) -> headline s ++ (concatMap (show' (level + 1)) list)
+			(Para s) -> [indent s]
+
+			where
+				indent :: String -> String
+				indent = ((concat $ take level $ repeat "  ") ++)
+		
+				headline :: String -> [String]
+				headline s = indent "" : if level >= length typoChars 
+					then [indent s ++":"]
+					else [indent s, indent (take (length s) (repeat (typoChars!!level)))]
+
+				typoChars = "*-'"
+		
+-- Functions
+
+version :: Version.Version
+version = Version.Version [0,1,0] []
+
+name :: String
+name = "CalDims"
+
+preludeText, welcomeText :: String
+preludeText = unlines
+        [ "# Time Units"
+        , "\\u s"
+        , "min := 60 s"
+        , "h := 60 min"
+        , "d := 24 h"
+        , "Hz := 1s^-1"
+        , ""
+        , "# Space Units"
+        , "\\u m"
+        , "l := (0.1 m)^3"
+        , ""
+        , "# Mass Units"
+        , "\\u kg"
+        , "t := 1000 kg"
+        , "u := 1.6605402 * 10^-27 kg"
+        , ""
+        , "# Molar mass"
+        , "\\u mol"
+        , ""
+        , "# Force"
+        , "N := 1m kg/s^2"
+        , ""
+        , "# Energy"
+        , "J := 1 N m"
+        , ""
+        , "# Power"
+        , "W := 1 J/s"
+        , ""
+        , "# Electro physics"
+        , "\\u A"
+        , "C := 1 A s"
+        , "V := 1 W/A"
+        , "F := 1 A s/V"
+        , "Ohm := 1 V/A"
+        , "H := 1 V s/A"
+        , ""
+        , "# Light"
+        , "\\u cd"
+        , ""
+        , "# Temperature"
+        , "\\u K"
+        , ""
+        , "# Constants"]
+
+welcomeText = name ++ " " ++ Version.showVersion version ++ "\n" ++ "License: GPL 3 (see the LICENSE file)\n\n" 
+	++ "Type in `\\?' to read the inline help.\n"
+
+helpText :: HelpTree
+helpText = Section (name ++ " help")
+	[ Section "Usage of the shell" 
+		[ Para "The shell is an infinite loop that accepts one line of user-input and processes it."
+		, Para "The input line syntax is: expr|command|fundef|unitdef|comment"
+		, Section "Expression to evaluate (expr)" 
+			[ Para "The syntax of an evaluation request is: expr ('|'(unit|expr|-|*|?))."
+			, Para "For detailed expression syntax see chapter `Expression syntax'."
+			, Section "Examples"
+				[ Para "(10000 m^2)^1%2                  -> 100 m (square root of 10000 m^2)"
+				, Para "7 d | h                          -> 168 h  (7 days are 168 hours)"
+				, Para "80W * 30d * 0.20EUR/kW/h | EUR   -> 11.52 EUR"
+				, Para "sin (pi/4) * 10 V                -> 7.071067811865475 V"]
+
+			, Section "Evaluation modifiers"
+				[ Para "expr | unit        -> converts expr to unit after evaluation"
+				, Para "expr1 | expr2      -> rewrite expr in terms of expr2"
+				, Para "expr | ?           -> try to find the minimal unit for expr"
+				, Para "expr | *           -> simply keep the unit that was evaluated"
+				, Para "expr | -           -> rewrite the evaluation in terms of basic units"
+				, Para []
+				, Para "Modifiers are optional, 'expr | *' and 'expr' are equivalent."]
+				
+			]
+		, Section "Shell command (command)"
+			[ Para "\\?             - display this help"
+			, Para "\\d  expr       - show unevaluated expression"
+			, Para "\\de expr       - just like `\\d expr'"
+			, Para "\\dn name       - show unit or function"
+			, Para "\\dp name       - show the dependencies and the reverse dependecies of a unit or function"
+			, Para "\\p  string     - print <string> to stdout."
+			, Para "\\r  name       - remove a function or unit."
+			, Para "\\rc name       - remove cascade - remove all entities that depend on <name> and <name> itself."
+			, Para "\\s             - print the state"
+			, Para "\\u  name       - add a basic unit"]
+
+		, Section "Function definition (fundef)"
+			[ Para "A function definition has the following syntax: name (name1:unit1, name2:unit2, ...) = expr"
+
+			, Section "Examples"
+				[ Para "t = 3 min"
+				, Para "volumen (radius:m) = pi * radius^3"
+				, Para "speed (distance:m, time:s) = distance / time"]
+			, Para ""
+			, Para "Units that have to follow a parameter and colon indicate the dimension of the parameter only,"
+			, Para "so 'duration(t1:min, t2:min)=t2-t1' and 'duration(t1:h, t2:d)=t2-t1' are totally equivalent."]
+
+
+		, Section "Unit definition (unitdef)"
+			[ Para "A unit definition has the following syntax: name:=expr"
+			, Section "Examples"
+				[ Para "mile := 1609.344 m"
+				, Para "min := 60 s"
+				, Para "h := 60 min"
+				, Para "mph := 1 mile/h"]
+			]
+
+		, Section "Comment line (comment)"
+			[ Para "You can add comment lines to your source files or comment out a line inside the shell."
+			, Para "A comment line has the following syntax: # string"
+			, Section "Example" [Para "# This is a comment"]
+			]
+		]
+
+	, Section "Command invocation"
+		[ Para "caldims [OPTION] <FILE>"
+		, Para "caldims           - start the shell and load the user's `prelude.cal'"
+		, Para "caldims <file>    - start the shell and load <file> instead of `prelude.cal'"
+		, Para "caldims --blank   - start the shell without loading a file"
+		, Para "caldims --echo    - echo every input line"
+		, Para "caldims --help    - display this help text"]
+
+	, Section "Expression syntax (expr)"
+		[ Para "Currently only arithmetic expressions are supported."
+		, Section "Examples"
+			[ Para "1+2            -> 3"
+			, Para "1m + 2m        -> 3 m"
+			, Para "1m * 2m        -> 2 m^2"]
+		
+		, Section "Builtin functions. All of these are dimensionless."
+			[ Para "pi             -> pi"
+			, Para "e              -> Euler number"
+			, Para "logBase (a, b) -> logarithm of a with base b"
+			, Para "log (a)        -> logarithm of a with base e"
+			, Para "exp (a)        -> expotential function (e^a)"
+			, Para ""
+			, Para "sin, cos, tan, asin, acos, atan, sinh, cosh, tanh, asinh, acosh, atanh"]
+
+		, Section "Syntax productions"
+			[ Section "An expression (expr) may be of one of the following forms"
+				[ Para "- expr"
+				, Para "expr + expr"
+				, Para "expr - expr"
+				, Para "expr * expr"
+				, Para "expr / expr"
+				, Para "expr ^ integer>"
+				, Para "(expr)"
+				, Para "number unit"
+				, Para "functionname"
+				, Para "functionname (arg1, arg2, ... )"]
+			, Section "A number can be"
+				[ Para "real"
+				, Para "integer%integer"]
+
+			, Section "A unit is one of"
+				[ Para "unit / unit"
+				, Para "unit unit"
+				, Para "(unit)"
+				, Para "unitname"
+				, Para "unitname ^ integer"]]]
+		
+	, Section "The `prelude.cal' file"
+		[ Para ("When a user starts " ++ name ++ " and `prelude.cal' cannot be found in the")
+		, Para "`data directory, then a standard prelude is created. It contains definitions of"
+		, Para "the SI base units and some derived units. You can replace or modify this file."]]
diff --git a/src/Language/CalDims/Types.hs b/src/Language/CalDims/Types.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/CalDims/Types.hs
@@ -0,0 +1,167 @@
+{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-}
+
+module Language.CalDims.Types 
+	( Name (..)
+	, MyParser
+	, Scope
+	, State (..)
+	, StateEntry (..)
+	, D
+	, R
+	, Conversion (..)
+	, Expr (..)
+	, BinOp (..)
+	, UniOp (..)
+	, Priority (..)
+	, Args
+	, Arg (..)
+	, Pretty (..)
+	, Dims (..)
+	, noDims
+	, EqM (..)
+	, AddM (..)
+	, SubM (..)
+	, MulM (..)
+	, DivM (..)
+	, ExpM (..)
+	, LogBaseM (..)
+	, NegateM (..)
+	, ExpotM (..)
+	, LogM (..)
+	, SqrtM (..)
+	, SinM (..)
+	, CosM (..)
+	, TanM (..)
+	, AsinM (..)
+	, AcosM (..)
+	, AtanM (..)
+	, SinhM (..)
+	, CoshM (..)
+	, TanhM (..)
+	, AsinhM (..)
+	, AcoshM (..)
+	, AtanhM (..)) where
+
+
+import Text.ParserCombinators.Parsec (GenParser)
+import qualified Data.Map as Map
+import Data.Ratio
+--import Data.Generics
+import Control.Monad.Error
+import qualified Data.List as List
+class Pretty a where
+	pretty :: a -> String
+
+instance Pretty Int where pretty i = show i
+instance Pretty a => Pretty [a] where
+	pretty [] = "[]"
+	pretty (a:l) = "[" ++ foldl (\x y -> x ++ ", " ++ y) (pretty a) (map pretty l) ++ "]"
+
+instance Pretty Char where pretty c = [c]
+
+
+instance Pretty Dims where
+        pretty (Dims a)
+                | null list = ""
+                | otherwise = tail (pretty' list)
+                where
+                        list = filter (\ (_, y) -> y /= 0) $ List.sort $ Map.toList a
+
+                        pretty' :: [(Name, R)] -> String
+                        pretty' [] = ""
+                        pretty' (el@(_, exp_):fs) = if exp_ > 0
+                                then ePretty el ++ pretty' fs
+                                else pretty' fs ++ " /" ++ ePretty el
+
+                        ePretty :: (Name, R) -> String
+                        ePretty (name, e) = let n = pretty name in
+                                " " ++ if abs e == 1 then n else n ++ "^" ++ (pretty $ abs e)
+
+
+
+data Conversion = Explicit Dims | InTermsOf Expr | Basic | Keep | Minimal deriving Show
+
+type D = Double
+type R = Ratio Integer
+
+newtype Name = Name {unName :: String} deriving (Eq, Show, Ord)
+instance Pretty Name where pretty (Name s) = s
+
+instance Pretty (Ratio Integer) where
+        pretty r = if d == 1 then (show n) else show . floating $ r where
+                d = denominator r
+                n = numerator r
+
+floating :: R -> D
+floating r = fromInteger (numerator r) / fromInteger (denominator r)
+
+
+type MyParser = GenParser Char State
+
+type Scope = Map.Map Name StateEntry
+
+data State = State
+        { getScope :: Scope
+        , getArgs :: Args
+        , getArgValues :: [(R, Dims)]
+        } deriving (Show)
+
+data StateEntry = Function Args Expr | Dimension Expr | BasicDimension | Builtin Args Expr
+        deriving (Show)
+
+
+data Expr = Bin BinOp Expr Expr | Uni UniOp Expr | ArgRef Arg
+        | Call Name [Expr] | Evaled (R, Dims) deriving (Show)
+
+data BinOp = Add | Sub | Mul | Div | Exp | LogBase
+        deriving (Eq, Show)
+
+data UniOp = Negate | Expot | Log | Sin | Cos | Tan | Asin | Acos | Atan
+        | Sinh | Cosh | Tanh | Asinh | Acosh | Atanh
+        deriving (Eq, Show)
+
+data Priority = P_Add |  P_Mul |  P_Exp | P_Negate | P_Elementary
+        deriving (Eq, Enum, Ord)
+
+type Args = [Arg]
+
+data Arg = Arg
+        { getArgName :: String -- This is not a Name because it does not reference a State-Entry.
+        , getArgNumber :: Int
+        , getArgType :: Dims
+        } deriving (Show, Ord, Eq)
+
+newtype Dims = Dims {unDims :: Map.Map Name R} deriving (Show, Ord, Eq)
+
+noDims :: Dims
+noDims  = Dims Map.empty
+
+
+class (Monad m) => EqM a m where (#==#) :: m a -> m a -> m Bool
+
+class (Monad m) => AddM a m where (#+#) :: m a -> m a -> m a
+class (Monad m) => SubM a m where (#-#) :: m a -> m a -> m a
+class (Monad m) => MulM a m where (#*#) :: m a -> m a -> m a
+class (Monad m) => DivM a m where (#/#) :: m a -> m a -> m a
+class (Monad m) => ExpM a m where (#^#) :: m a -> m a -> m a
+class (Monad m) => LogBaseM a m where (#~#) :: m a -> m a -> m a
+
+class (Monad m) => NegateM a m where negateM :: m a -> m a
+class (Monad m) => ExpotM a m where expM :: m a -> m a
+class (Monad m) => LogM a m where logM :: m a -> m a
+class (Monad m) => SqrtM a m where sqrtM :: m a -> m a
+class (Monad m) => SinM a m where sinM :: m a -> m a
+class (Monad m) => CosM a m where cosM :: m a -> m a
+class (Monad m) => TanM a m where tanM :: m a -> m a
+class (Monad m) => AsinM a m where asinM :: m a -> m a
+class (Monad m) => AcosM a m where acosM :: m a -> m a
+class (Monad m) => AtanM a m where atanM :: m a -> m a
+class (Monad m) => SinhM a m where sinhM :: m a -> m a
+class (Monad m) => CoshM a m where coshM :: m a -> m a
+class (Monad m) => TanhM a m where tanhM :: m a -> m a
+class (Monad m) => AsinhM a m where asinhM :: m a -> m a
+class (Monad m) => AcoshM a m where acoshM :: m a -> m a
+class (Monad m) => AtanhM a m where atanhM :: m a -> m a
+
+
+
diff --git a/tool/Main.hs b/tool/Main.hs
new file mode 100644
--- /dev/null
+++ b/tool/Main.hs
@@ -0,0 +1,6 @@
+module Main (main) where
+
+import Language.CalDims.Program
+
+main :: IO()
+main = defMain