Imports updated

package.json

@@ -5,10 +5,11 @@
     "synopsis": "A library to use Constraint Handling Rules in Curry programs",
     "category": [ "Constraints" ],
     "dependencies": {
-        "flatcurry": ">= 2.0.0",
-        "prolog"   : ">= 1.0.0",
-        "wl-pprint": ">= 0.0.1",
-        "xml"      : ">= 2.0.0"
+        "flatcurry"    : ">= 2.0.0",
+        "prolog"       : ">= 1.0.0",
+        "redblacktree" : ">= 0.0.1",
+        "wl-pprint"    : ">= 0.0.1",
+        "xml"          : ">= 2.0.0"
     },
     "exportedModules": [ "CHR" ],
     "description": "This library an implementation of Constraints Handling

src/CHR.curry

@@ -32,13 +32,13 @@ import FlatCurry.Files
 import FlatCurry.Goodies
 import FlatCurry.Pretty  ( defaultOptions, ppTypeExp )
 import List
-import SetRBT
 import Unsafe -- for tracing
 import XML
 
-import Text.Pretty       ( showWidth )
+import Data.Set.RBTree   ( SetRBT, member, empty, insert )
 import Prolog.Types
 import Prolog.Show       ( showPlClause, showPlGoals )
+import Text.Pretty       ( showWidth )
 
 -------------------------------------------------------------------------------
 -- Operator definitions for writing CHRs:
@@ -265,13 +265,13 @@ solveCHR prules goal =
 type History = SetRBT ([Int],Int) -- entry: constraint indices and rule index
 
 emptyHistory :: Ord a => SetRBT a
-emptyHistory  = emptySetRBT (<=)
+emptyHistory = empty
 
-extendHistory :: a -> SetRBT a -> SetRBT a
-extendHistory = insertRBT
+extendHistory :: Ord a => a -> SetRBT a -> SetRBT a
+extendHistory = insert
 
-inHistory :: a -> SetRBT a -> Bool
-inHistory     = elemRBT
+inHistory :: Ord a => a -> SetRBT a -> Bool
+inHistory = member
 
 ------------------------------------------------------------------------
 --- Interpret CHR rules (parameterized over domain variables)