diff --git a/Satchmo/Binary.hs b/Satchmo/Binary.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Binary.hs
@@ -0,0 +1,128 @@
+{-# language MultiParamTypeClasses #-}
+
+module Satchmo.Binary 
+
+( Number, width, number, fixed
+, add, times
+, equals
+)
+
+where
+
+import Prelude hiding ( and, or, not )
+
+import qualified Satchmo.Code as C
+import Satchmo.Boolean
+import Satchmo.Counting
+
+type Booleans = [ Boolean ]
+
+data Number = Number 
+            { encode :: Booleans -- lsb first
+            , decode :: C.Decoder Integer
+            }
+
+instance C.Decode Number Integer where
+    decode = decode
+
+width :: Number -> Int
+width n = length $ encode n
+
+-- | declare a number variable (bit width)
+number :: Int -> SAT Number
+number w = do
+    xs <- sequence $ replicate w boolean
+    return $ make xs
+
+make :: [ Boolean ] -> Number
+make xs = Number
+           { encode = xs
+           , decode = do ys <- mapM C.decode xs ; return $ fromBinary ys
+           }
+
+fromBinary :: [ Bool ] -> Integer
+fromBinary xs = foldr ( \ x y -> 2*y + if x then 1 else 0 ) 0 xs
+
+toBinary :: Int -> Integer -> [ Bool ]
+toBinary 0 0 = []
+toBinary b n | b > 0 = 
+    let (d,m) = divMod n 2
+    in  toEnum ( fromIntegral m ) : toBinary (b-1) d
+
+-- | declare a number constant (bit width, value)
+fixed :: Int -> Integer -> SAT Number
+fixed b n = do
+    xs <- mapM constant $ toBinary b n
+    return $ make xs
+
+-- | result width is 1 + largest argument width
+add :: Number -> Number -> SAT Number
+add ( Number { encode = xs } ) ( Number { encode = ys } ) = do
+    false <- constant False
+    ( zs, carry ) <- add_with_carry false xs ys
+    return $ make $ zs ++ [carry]
+
+-- | result width is largest argument width
+-- if overflow, then unsatisfiable
+restricted_add :: Number -> Number -> SAT Number 
+restricted_add a b = do
+    c <- add a b
+    restricted ( max (width a) (width b)) c
+
+-- | give only lower k bits, upper bits must be zero,
+-- (else unsatisfiable)
+restricted :: Int -> Number -> SAT Number
+restricted w ( Number { encode = xs } ) = do
+    let ( low, high ) = splitAt w xs
+    sequence $ do x <- high ; return $ assert [ not x ]
+    return $ make low
+
+-- | result has max length of both inputs
+add_with_carry :: Boolean 
+               -> Booleans -> Booleans
+               -> SAT ( Booleans, Boolean )
+add_with_carry cin [] [] = return ( [], cin )
+add_with_carry cin (x:xs) [] = do
+    z <- xor [ cin, x ]
+    c <- and [ cin, x ]
+    ( zs, cout ) <- add_with_carry c xs []
+    return ( z : zs, cout )
+add_with_carry cin [] (y:ys) = do
+    add_with_carry cin (y:ys) []
+add_with_carry cin (x:xs ) (y:ys) = do
+    z  <- xor [ cin, x, y ]
+    c <- atleast 2 [ cin, x, y ]
+    ( zs, cout ) <- add_with_carry c xs ys
+    return ( z : zs, cout )
+
+times :: Number -> Number -> SAT Number
+times ( Number { encode = [x] } ) ys = times1 x ys
+times ( Number { encode = x:xs } ) ys = do
+    xys  <- times1 x ys
+    xsys <- times (make xs) ys
+    zs <- shift xsys
+    add xys zs
+
+-- | multiply by 2
+shift :: Number -> SAT Number
+shift ( Number { encode = xs } ) = do
+    false <- constant False 
+    return $ make $ false : xs
+
+times1 :: Boolean -> Number -> SAT Number
+times1 x ( Number { encode = ys } ) = do
+    zs <- mapM ( \ y -> and [x,y] ) ys
+    return $ make zs
+
+equals :: Number -> Number -> SAT Boolean
+equals ( Number { encode = xs } ) ( Number { encode = ys } ) = do
+    equals' xs ys
+
+equals' :: Booleans -> Booleans -> SAT Boolean
+equals' [] [] = constant True
+equals' (x:xs) (y:ys) = do
+    z <- xor [x, y]
+    rest <- equals' xs ys
+    and [ not z, rest ]
+equals' xs [] = and $ map not xs
+equals' [] ys = and $ map not ys
diff --git a/Satchmo/Boolean.hs b/Satchmo/Boolean.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Boolean.hs
@@ -0,0 +1,14 @@
+module Satchmo.Boolean 
+
+( SAT
+, module Satchmo.Boolean.Data
+, module Satchmo.Boolean.Op
+) 
+
+where
+
+import qualified Prelude
+
+import Satchmo.Internal
+import Satchmo.Boolean.Data
+import Satchmo.Boolean.Op
diff --git a/Satchmo/Boolean/Data.hs b/Satchmo/Boolean/Data.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Boolean/Data.hs
@@ -0,0 +1,73 @@
+{-# language MultiParamTypeClasses #-}
+
+module Satchmo.Boolean.Data 
+
+( Boolean, boolean, constant
+, not, assert, monadic
+)
+
+where
+
+import Prelude hiding ( not )
+import qualified Prelude
+
+import qualified Satchmo.Code as C
+
+import Satchmo.Data 
+import Satchmo.Internal
+
+import Data.Map ( Map )
+import qualified Data.Map as M
+import Data.Maybe ( fromJust )
+import Data.List ( partition )
+
+import Control.Monad.Reader
+
+data Boolean = Boolean
+             { encode :: Literal
+             , decode :: C.Decoder Bool
+             }
+     | Constant { value :: Bool }
+
+isConstant :: Boolean -> Bool
+isConstant ( Constant {} ) = True
+isConstant _ = False
+
+instance C.Decode Boolean Bool where 
+    decode b = case b of
+        Boolean {} -> decode b
+        Constant {} -> return $ value b
+
+boolean :: SAT Boolean
+boolean = do
+    x <- fresh
+    return $ Boolean 
+           { encode = x
+           , decode = asks $ \ fm -> fromJust $ M.lookup x fm
+           }
+
+constant :: Bool -> SAT Boolean
+constant v = do
+    return $ Constant { value = v } 
+
+not :: Boolean -> Boolean
+not b = case b of
+    Boolean {} -> Boolean 
+      { encode = nicht $ encode b
+      , decode = do x <- decode b ; return $ Prelude.not x
+      }
+    Constant {} -> Constant { value = Prelude.not $ value b }
+
+assert :: [ Boolean ] -> SAT ()
+assert bs = do
+    let ( con, uncon ) = partition isConstant bs
+    let cval = Prelude.or $ map value con
+    when ( Prelude.not cval ) $ emit $ clause $ map encode uncon
+
+monadic :: Monad m
+        => ( [ a ] -> m b )
+        -> ( [ m a ] -> m b )
+monadic f ms = do
+    xs <- sequence ms
+    f xs
+
diff --git a/Satchmo/Boolean/Op.hs b/Satchmo/Boolean/Op.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Boolean/Op.hs
@@ -0,0 +1,41 @@
+module Satchmo.Boolean.Op 
+
+( constant
+, and, or, xor
+, monadic
+)
+
+where
+
+import Prelude hiding ( and, or, not )
+
+import Satchmo.Internal
+import Satchmo.Code
+import Satchmo.Boolean.Data
+
+and :: [ Boolean ] -> SAT Boolean
+and xs = do
+    y <- boolean
+    sequence $ do
+        x <- xs
+        return $ assert [ not y, x ]
+    assert $ y : map not xs
+    return y
+
+or :: [ Boolean ] -> SAT Boolean
+or xs = do
+    y <- and $ map not xs
+    return $ not y
+
+xor :: [ Boolean ] -> SAT Boolean
+xor [x] = return x
+xor (x : xs) = do
+    rest <- xor xs
+    xor2 x rest
+
+xor2 :: Boolean -> Boolean -> SAT Boolean
+xor2 x y = do
+    a <- and [ x, not y ]
+    b <- and [ not x, y ]
+    or [ a, b ]
+
diff --git a/Satchmo/Code.hs b/Satchmo/Code.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Code.hs
@@ -0,0 +1,39 @@
+{-# language MultiParamTypeClasses, FunctionalDependencies, UndecidableInstances #-}
+
+module Satchmo.Code 
+
+( Decode (..)
+, Decoder
+)
+
+where
+
+import Satchmo.Data
+
+
+import Data.Map ( Map )
+import qualified Data.Map as M
+import Data.Array
+
+import Control.Monad.Reader
+
+
+class Decode c a | c -> a where decode :: c -> Decoder a
+
+type Decoder a = Reader ( Map Literal Bool ) a
+
+
+instance ( Decode c a, Decode d b ) => Decode ( c,d) (a,b) where
+    decode (c,d) = do a <- decode c; b <- decode d; return ( a,b)
+
+instance ( Decode c a ) => Decode [c] [a] where
+    decode = mapM decode 
+
+instance (Ix i, Decode c a) => Decode ( Array i c) ( Array i a ) where
+    decode x = do
+        pairs <- sequence $ do
+            (i,e) <- assocs x
+            return $ do
+                f <- decode e
+                return (i,f)
+        return $ array (bounds x) pairs
diff --git a/Satchmo/Counting.hs b/Satchmo/Counting.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Counting.hs
@@ -0,0 +1,73 @@
+module Satchmo.Counting 
+
+( atleast
+, atmost
+, exactly
+)
+
+where
+
+import Prelude hiding ( and, or, not )
+
+import Satchmo.Boolean
+
+atleast_block :: Int -> [ Boolean ] -> SAT [ Boolean ]
+atleast_block k [] = do
+    t <- constant True
+    f <- constant False
+    return $ t : replicate k f
+atleast_block k (x:xs) = do
+    cs <- atleast_block k xs
+    sequence $ do
+        i <- [ 0 .. k ]
+        return $ if i == 0 then return $ cs !! 0
+                 else do
+                     p <- and [ x, cs !! (i-1) ]
+                     or [ cs !! i, p ]
+
+atleast :: Int -> [ Boolean ] -> SAT Boolean
+atleast k xs = do
+    cs <- atleast_block k xs
+    return $ cs !! k
+        
+
+atmost_block :: Int -> [ Boolean ] -> SAT [ Boolean ]
+atmost_block k [] = do
+    t <- constant $ True
+    return $ replicate (k+1) t
+atmost_block k (x:xs) = do
+    cs <- atmost_block k xs
+    sequence $ do
+        i <- [ 0 .. k ]
+        return $ do
+            f <- constant False
+            p <- and [ x, if i > 0 then cs !! (i-1) else f ]
+            q <- and [ not x, cs !! i ]
+            or [ p, q ]
+
+atmost :: Int -> [ Boolean ] -> SAT Boolean
+atmost k xs = do
+    cs <- atmost_block k xs
+    return $ cs !! k
+        
+
+exactly_block :: Int -> [ Boolean ] -> SAT [ Boolean ]
+exactly_block k [] = do
+    t <- constant True
+    f <- constant False
+    return $ t : replicate k f
+exactly_block k (x:xs) = do
+    cs <- exactly_block k xs
+    sequence $ do
+        i <- [ 0 .. k ]
+        return $ do
+            f <- constant False
+            p <- and [ x, if i > 0 then cs !! (i-1) else f ]
+            q <- and [ not x, cs !! i ]
+            or [ p, q ]
+
+exactly :: Int -> [ Boolean ] -> SAT Boolean
+exactly k xs = do
+    cs <- exactly_block k xs
+    return $ cs !! k
+        
diff --git a/Satchmo/Data.hs b/Satchmo/Data.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Data.hs
@@ -0,0 +1,42 @@
+module Satchmo.Data 
+
+( CNF, cnf, clauses
+, Clause, clause, literals
+, Literal, literal, nicht
+)
+
+where
+
+import Control.Monad.State.Strict
+
+data CNF     = CNF { clauses :: [ Clause  ] }
+
+instance Show CNF where
+    show ( CNF cs ) = unlines $ map show cs
+
+cnf :: [ Clause ] -> CNF
+cnf cs = CNF cs
+
+
+data Clause  = Clause { literals :: [ Literal ] }
+
+instance Show Clause where
+    show ( Clause xs ) = unwords ( map show xs ++ [ "0" ] )
+
+clause :: [ Literal ] -> Clause
+clause ls = Clause { literals = ls }
+
+
+data Literal = Literal Int 
+    deriving ( Eq, Ord )
+
+instance Show Literal where 
+    show ( Literal i ) = show i
+
+literal :: Int -> Literal
+literal i | i /= 0 = Literal i
+
+
+nicht :: Literal -> Literal
+nicht ( Literal i ) = Literal $ negate i
+
diff --git a/Satchmo/Internal.hs b/Satchmo/Internal.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Internal.hs
@@ -0,0 +1,50 @@
+module Satchmo.Internal 
+
+( SAT
+, fresh, emit
+, sat
+)
+
+where
+
+import Satchmo.Data
+
+import Control.Monad.State.Strict
+import Control.Monad.Writer.Strict
+
+data Accu = Accu 
+          { next :: ! Int
+          , size :: ! Int
+          }
+
+start :: Accu
+start = Accu 
+      { next = 1
+      , size = 0
+      }
+
+type SAT a = WriterT [ Clause ] (State Accu) a
+
+sat :: SAT a -> ( String, a )
+sat m = 
+    let ~( ~(a,w), accu) = runState ( runWriterT m ) start
+    in  ( unlines $ unwords [ "p", "cnf", show ( next accu - 1), show ( size accu ) ]
+                    : map show w
+        , a
+        )
+    
+fresh :: SAT Literal
+fresh = do
+    a <- get
+    put $ a { next = next a + 1 }
+    return $ literal $ next a
+
+emit :: Clause -> SAT ()
+emit clause = do
+    a <- get
+    tell [ clause ]
+    put $ a 
+        { size = size a + 1 
+        }
+
+
diff --git a/Satchmo/Solve.hs b/Satchmo/Solve.hs
new file mode 100644
--- /dev/null
+++ b/Satchmo/Solve.hs
@@ -0,0 +1,49 @@
+module Satchmo.Solve
+
+( solve
+, Decoder
+)
+
+where
+
+import Satchmo.Data
+import Satchmo.Code
+import Satchmo.Internal
+
+import Data.Map ( Map )
+import qualified Data.Map as M
+
+import Control.Monad.State
+import Control.Monad.Reader
+import System.Process
+
+
+solve :: SAT ( Decoder a )
+    -> IO ( Maybe a )
+solve build = do
+    let (s, a) = sat build
+    mfm <- run s
+    case mfm of
+        Nothing -> do
+            putStrLn "not satisfiable"
+            return Nothing
+        Just fm -> do
+            putStrLn "satisfiable"
+            -- print fm
+            return $ Just $ runReader a fm
+                
+run :: String -> IO ( Maybe ( Map Literal Bool ) )
+run cs = do
+    let debug = False
+    if debug 
+       then putStrLn cs
+       else putStrLn $ head $ lines cs
+    ( code, stdout, stderr ) <- 
+        readProcessWithExitCode "minisat" [ "/dev/stdin", "/dev/stdout" ] cs
+    when debug $ putStrLn stdout
+    case lines stdout of
+        "SAT" : xs : _ -> return $ Just $ M.fromList $ do
+            x <- takeWhile ( /= 0 ) $ map read $ words xs
+            let l = literal $ abs x
+            return ( l, x > 0 )
+        _ -> return $ Nothing
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/TODO b/TODO
new file mode 100644
--- /dev/null
+++ b/TODO
@@ -0,0 +1,8 @@
+* minisat needs to be in the $PATH (for execution),
+  but this is not checked during installation.
+
+* actually, should provide several backends (separate package satchmo-minisat etc.,
+  similar as hsql with backends like hsql-mysql etc.)
+
+* need timeout handler for calling the SAT solver.
+
diff --git a/gpl-2.0.txt b/gpl-2.0.txt
new file mode 100644
--- /dev/null
+++ b/gpl-2.0.txt
@@ -0,0 +1,339 @@
+		    GNU GENERAL PUBLIC LICENSE
+		       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+			    Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
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+
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+
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+
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+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/satchmo.cabal b/satchmo.cabal
new file mode 100644
--- /dev/null
+++ b/satchmo.cabal
@@ -0,0 +1,30 @@
+Name:           satchmo
+Version:        1.0
+License:        GPL
+License-file:	gpl-2.0.txt
+Author:         Johannes Waldmann
+Maintainer:	Johannes Waldmann
+Homepage:       http://dfa.imn.htwk-leipzig.de/satchmo/
+Category:       Testing
+Synopsis:       SAT encoding monad
+description:	Encoding for boolean and integral constraints into CNF-SAT.
+		The encoder is provided as a State monad (hence the "mo" in "satchmo").
+		Requires SAT solver minisat installed.
+Build-depends:  mtl, process, containers, base, array
+Exposed-modules:
+        Satchmo.Boolean
+        Satchmo.Solve
+	Satchmo.Counting
+	Satchmo.Binary
+	Satchmo.Code
+Other-modules:
+        Satchmo.Boolean.Data
+	Satchmo.Boolean.Op
+	Satchmo.Internal
+	Satchmo.Data
+hs-source-dirs:	.
+extra-source-files: test/Binary.hs  test/HC.hs      test/Schur.hs
+		    test/Cage.hs    test/Ramsey.hs  test/VC.hs
+		    TODO
+extensions: 
+build-type: Simple
diff --git a/test/Binary.hs b/test/Binary.hs
new file mode 100644
--- /dev/null
+++ b/test/Binary.hs
@@ -0,0 +1,76 @@
+-- | run tests like this: "solve test2"
+
+import Prelude hiding ( not )
+
+import Satchmo.Boolean
+import Satchmo.Code
+import Satchmo.Binary
+import Satchmo.Solve
+
+
+assert_positive x = do 
+    n <- fixed 0 0 
+    e <- equals n x 
+    assert [ not e ]
+
+assert_equals x y = do 
+    e <- equals x y 
+    assert [ e ]
+
+assert_lt x y = do 
+    d <- number $ width y
+    assert_positive d
+    xd <- add x d
+    assert_equals xd y
+
+test1 = do 
+    x <- number 4 
+    y <- fixed 4 12 
+    assert_equals x y
+    return $ decode (x,y)
+
+test2 = do 
+    x <- fixed 5 3
+    y <- fixed 5 9
+    z <- add x y
+    return $ decode [x,y,z]
+
+test3 = do 
+    x <- number 5 
+    xx <- add x x
+    xxx <- add xx x
+    y <- fixed 5 15 
+    assert_equals xxx y 
+    return $ decode [ x, y ]
+
+test4 = do 
+    x <- number  8
+    y <- number  8
+    xy <- times x y
+    z <- fixed 8 63
+    assert_equals xy z
+    return $ decode [x, y, z]
+
+test5 = do 
+    x <- number  8
+    y <- number  8
+    xy <- times x y
+    z <- fixed 10 1001
+    assert_equals xy z
+    return $ decode [x, y, z]
+
+ramanujan = do
+    let bits = 5
+    a <- number  bits
+    b <- number  bits
+    c <- number  bits
+    d <- number  bits
+
+    assert_lt a c ; assert_lt c d ; assert_lt d b
+
+    let cube x = do x2 <- times x x ; times x2 x
+    a3 <- cube a; b3 <- cube b; ab <- add a3 b3
+    c3 <- cube c; d3 <- cube d; cd <- add c3 d3
+    assert_equals ab cd
+
+    return $ decode [a,b,c,d]
diff --git a/test/Cage.hs b/test/Cage.hs
new file mode 100644
--- /dev/null
+++ b/test/Cage.hs
@@ -0,0 +1,58 @@
+import Prelude hiding ( not )
+
+import Satchmo.Relation
+import Satchmo.Code
+import Satchmo.Boolean
+import Satchmo.Counting
+import Satchmo.Solve
+
+import Data.List ( inits, tails )
+import System.Environment
+
+-- | command line arguments: r g n
+-- program looks for a (r,g) cage:
+-- r-regular graph with girth g on n nodes
+
+main :: IO ()
+main = do
+    argv <- getArgs
+    let [ r, g, n ] = map read argv
+    Just a <- solve $ cage r g n
+    putStrLn $ table a
+
+type Graph = Relation Int Int
+
+cage r g n = do
+    a <- relation ((1,1),(n,n))
+    monadic assert [ symmetric a ]
+    monadic assert [ irreflexive a ]
+    monadic assert [ regular r a ]
+    girth_at_least g a
+    return $ decode a
+
+girth_at_least :: Int -> Graph -> SAT ()
+girth_at_least k g = sequence_ $ do
+    let ((lo,_),(hi,_)) = bounds g
+    c <- [ 3 .. k-1 ]
+    xs <- sublists c [lo .. hi]
+    return $ assert_no_circle xs g
+    
+assert_no_circle xs g = 
+    assert $ do 
+        (x,y) <- zip xs $ rotate 1 xs
+        return $ not $ g ! (x,y)
+            
+sublists :: Int -> [a] -> [[a]]
+sublists 0 xs = return []
+sublists k xs = do
+    ( pre, this : post ) <- splits xs
+    that <- sublists (k-1) $ pre ++ post
+    return $ this : that
+
+splits :: [a] -> [ ([a],[a]) ]
+splits xs = zip ( inits xs ) ( tails xs )
+
+rotate :: Int -> [a] -> [a]
+rotate k xs = 
+    let ( pre, post ) = splitAt k xs
+    in  post ++ pre
diff --git a/test/HC.hs b/test/HC.hs
new file mode 100644
--- /dev/null
+++ b/test/HC.hs
@@ -0,0 +1,76 @@
+{-# language ScopedTypeVariables #-}
+
+import Prelude hiding ( not )
+import qualified Prelude
+
+import Satchmo.Relation
+import Satchmo.Code
+import Satchmo.Boolean
+import Satchmo.Counting
+import Satchmo.Solve
+
+import Data.List (sort)
+import qualified Data.Array as A
+import Control.Monad ( guard, when )
+import System.Environment
+
+-- | command line arguments: m n
+-- compute knight's tour on  m x n  chess board
+
+main :: IO ()
+main = do
+    argv <- getArgs
+    let [ m, n ] = map read argv
+    Just a <- solve $ tour m n
+    putStrLn $ unlines $ do
+         let ((u,l),(o,r)) = A.bounds a
+         x <- [u .. o]
+         return $ unwords $ do 
+             y <- [ l ..r ]
+             return $ fill 4 $ show $ a A.! (x,y)
+
+fill k cs = replicate (k - length cs) ' ' ++ cs
+
+tour m n = do
+    let s = m * n
+    p :: Relation Int (Int,Int) <- bijection ((1,(1,1)), (s,(m,n)))
+    sequence_ $ do
+        (i,j) <- zip [1..s] $ rotate 1 [1..s]
+        a <- A.range ((1,1),(m,n))
+        return $ do
+            assert $ not ( p!(i,a)) : do
+                b <- A.range ((1,1),(m,n))
+                guard $ reaches a b
+                return $ p ! (j,b) 
+            assert $ not ( p!(j,a)) : do
+                b <- A.range ((1,1),(m,n))
+                guard $ reaches a b
+                return $ p ! (i,b) 
+    return $ do
+        a <- decode p
+        return $ A.array ((1,1),(m,n)) $ do
+            ((i,p),True) <- A.assocs a
+            return (p,i)
+
+bijection :: (A.Ix a, A.Ix b) 
+                   => ((a,b),(a,b)) 
+                   -> SAT ( Relation a b )
+bijection bnd = do
+    let ((u,l),(o,r)) = bnd
+    a <- relation bnd
+    sequence_ $ do
+        x <- A.range (u,o)
+        return $ monadic assert $ return $ exactly 1 $ do y <- A.range (l,r) ; return $ a!(x,y)
+    sequence_ $ do
+        y <- A.range (l,r)
+        return $ monadic assert $ return $ exactly 1 $ do x <- A.range (u,o) ; return $ a!(x,y)
+    return a                                                   
+
+reaches (px,py) (qx,qy) = 
+    5 == (px - qx)^2 + (py - qy)^2
+
+rotate :: Int -> [a] -> [a]
+rotate k xs = 
+    let ( pre, post ) = splitAt k xs
+    in  post ++ pre
+    
diff --git a/test/Ramsey.hs b/test/Ramsey.hs
new file mode 100644
--- /dev/null
+++ b/test/Ramsey.hs
@@ -0,0 +1,83 @@
+import Prelude hiding ( not )
+import qualified Prelude
+
+import Satchmo.Relation
+import Satchmo.Code
+import Satchmo.Boolean
+import Satchmo.Counting
+import Satchmo.Solve
+
+import Data.List ( inits, tails )
+import Data.Ix
+import qualified Data.Array as A
+import Control.Monad ( forM, guard )
+import System.Environment
+
+-- | command line arguments: c_1 .. c_k n
+-- program prints graph g that proves
+-- R(c_1, .., c_k) > n
+
+main :: IO ()
+main = do
+    argv <- fmap ( map read ) getArgs
+    let cs = init argv
+        n  = last argv
+    Just a <- solve $ ramsey cs n
+    print a
+
+type Graph = Relation Int Int
+
+ramsey cs n = do
+    cols <- sequence $ replicate (length cs) $ do
+        r <- relation ((1,1),(n,n))
+        monadic assert [ symmetric r ]
+        monadic assert [ irreflexive r ]
+        return r
+    circular_colouring ( n `div` length cs ) cols
+    each_edge_is_coloured n cols
+    forM ( zip cs cols ) no_monochromatic_clique
+    return $ do
+        ds <- mapM decode cols
+        return $ do
+            i <- range ((1,1),(n,n))
+            let c = length $ takeWhile Prelude.not $ do d <- ds ; return $ d A.! i
+            return ( i, c )
+
+circular_colouring period cols = sequence_ $ do
+    (col, col') <- zip cols $ rotate 1 cols
+    x @ (p,q) <- indices col
+    let y = (p+period,q+period)
+    guard $ inRange ( bounds col ) y
+    return $ do
+        assert [ not $ col ! x, col' ! y ]
+
+rotate :: Int -> [a] -> [a]
+rotate k xs = 
+    let ( pre, post ) = splitAt k xs
+    in  post ++ pre
+
+each_edge_is_coloured n cols = sequence_ $ do
+    (p,q) <- range ((1,1),(n,n))
+    guard $ p < q
+    return $ assert $ do 
+            col <- cols
+            return $ col ! (p,q)
+
+no_monochromatic_clique (c, col) = sequence_ $ do
+    let ((lo,_),(hi,_)) = bounds col
+    xs <- ordered_sublists c [lo .. hi]
+    return $ assert $ do
+        x : ys <- tails xs
+        y <- ys
+        return $ not $ col!(x,y)
+
+ordered_sublists :: Int -> [a] -> [[a]]
+ordered_sublists 0 xs = return []
+ordered_sublists k xs = do
+    ( pre, this : post ) <- splits xs
+    that <- ordered_sublists (k-1) $ post
+    return $ this : that
+
+splits :: [a] -> [ ([a],[a]) ]
+splits xs = zip ( inits xs ) ( tails xs )
+
diff --git a/test/Schur.hs b/test/Schur.hs
new file mode 100644
--- /dev/null
+++ b/test/Schur.hs
@@ -0,0 +1,65 @@
+import Prelude hiding ( not, or, and )
+
+import Satchmo.Relation
+import Satchmo.Code
+import Satchmo.Boolean
+import Satchmo.Counting
+import Satchmo.Solve
+
+import Data.List ( inits, tails )
+import qualified Data.Array as A
+import System.Environment
+import Control.Monad ( guard, forM_ )
+
+-- | command line arguments: c n
+-- program looks for sum-free c-colouring of [1 .. n]
+
+main :: IO ()
+main = do
+    argv <- getArgs
+    let [ c, n ] = map read argv
+    Just a <- solve $ schur c n
+    putStrLn $ table a
+    print $ do
+        o <- [ 1 .. c ]
+        return ( o, length $ do i <- [ 1 .. n ]; guard $ a A.! (i,o) )
+
+schur c n = do
+    col <- relation ((1,1),(n,c))
+    each_number_coloured col
+    sum_free_colouring col
+    return $ decode col
+
+periodic p col = sequence_ $ do
+    let ((1,1),(n,c)) = bounds col
+    x <- [ 1 .. n ]
+    let y = x + p
+    guard $ y <= n
+    o <- [ 1 .. c ]
+    let p = 1 + o `mod` c
+    return $ assert [ not $ col!(x,o), col!(y,p) ]
+
+each_number_coloured col = sequence_ $ do
+    let ((1,1),(n,c)) = bounds col
+    x <- [ 1 .. n ]
+    return $ assert $ do o <- [1 .. c]; return $ col!(x,o)
+
+sum_free_colouring col = sequence_ $ do
+    let ((1,1),(n,c)) = bounds col
+    x <- [ 1 .. n ]
+    y <- [ x .. n ]
+    let z = (x + y) `mod` (n+1)
+    guard $ z <= n
+    guard $ 1 <= z
+    o <- [1 .. c]
+    return $ assert $ do 
+        p <- [ x, y, z ]
+        return $ not $ col!(p,o)
+
+evenly_distributed col = do
+    let ((1,1),(n,c)) = bounds col
+        d = n `div` c
+    forM_ [ 1 .. c ] $ \ o -> do
+        a <- atleast d $ do i <- [ 1 .. n ] ; return $ col!(i,o)
+        assert [a]
+
diff --git a/test/VC.hs b/test/VC.hs
new file mode 100644
--- /dev/null
+++ b/test/VC.hs
@@ -0,0 +1,37 @@
+import Prelude hiding ( not )
+
+import Satchmo.Relation
+import Satchmo.Code
+import Satchmo.Boolean
+import Satchmo.Counting
+import Satchmo.Solve
+
+import Control.Monad ( guard )
+import System.Environment
+
+-- | command line arguments: n s
+-- compute vertex cover of size <= s for knight's graph on  n x n  chess board
+
+main :: IO ()
+main = do
+    argv <- getArgs
+    let [ n, s ] = map read argv
+    Just a <- solve $ knight n s
+    putStrLn $ table a
+
+knight n s = do
+    a <- relation ((1,1),(n,n))
+    m <- atmost s $ do i <- indices a ; return $ a ! i
+    assert [m]
+    sequence_ $ do
+        p <- indices a
+        return $ assert $ do
+            q <- indices a
+            guard $ p == q || reaches p q
+            return $ a!q
+    return $ decode a
+        
+reaches (px,py) (qx,qy) = 
+    5 == (px - qx)^2 + (py - qy)^2
+
+