fix bug in partitions function

src/splines/Math/Monomial.hs

@@ -5,8 +5,6 @@
 {-# LANGUAGE TemplateHaskell       #-}
 {-# LANGUAGE UndecidableInstances  #-}
 
-{-# OPTIONS_GHC -ddump-splices -ddump-to-file #-}
-
 module Math.Monomial
   ( Mon(..)
   , MonomialBasis(..), Deg, Vars
@@ -188,27 +186,30 @@ partitions :: forall k n
            .  Word    -- ^ number of parts
            -> Mon k n -- ^ monomial to sum to
            -> [ [ ( Mon k n, Word ) ] ]
-partitions n_parts0 mon0 = go n_parts0 mon0 mon0
+partitions n_parts0 mon0 = go n_parts0 Nothing mon0
   where
-    go :: Word -> Mon k n -> Mon k n -> [ [ ( Mon k n , Word ) ] ]
+    go :: Word -> Maybe ( Mon k n ) -> Mon k n -> [ [ ( Mon k n , Word ) ] ]
     go 0 _ mon
       | isZeroMonomial mon
       = [ [] ]
       | otherwise
       = []
-    go 1 maxSub mon
+    go 1 mbMaxMon mon
       |  isZeroMonomial mon
-      || mon >= maxSub
+      || case mbMaxMon of { Just maxMon -> mon >= maxMon ; _ -> False }
       = []
       | otherwise
       = [ [ ( mon, 1 ) ] ]
-    go n_parts maxSub mon
+    go n_parts mbMaxMon mon
       = [ ( part, l ) : parts
         | ( part, l_max ) <- subs mon
         , not ( isZeroMonomial part ) -- parts must be non-empty
-        , part < maxSub               -- use a total ordering on monomials to ensure uniqueness
+        -- use a total ordering on monomials to ensure uniqueness
+        , case mbMaxMon of
+            Just maxMon -> part < maxMon
+            Nothing     -> True
         , l <- [ 1 .. min n_parts l_max ]
-        , parts <- go ( n_parts - l ) part ( subPart l mon part )
+        , parts <- go ( n_parts - l ) ( Just part ) ( subPart l mon part )
         ]
 
 subPart :: Word -> Mon k n -> Mon k n -> Mon k n