beginning of my own HList with type families...

diff --git a/Data/HList.hs b/Data/HList.hs
new file mode 100644 (file)
index 0000000..77ad6cc
--- /dev/null
+++ b/Data/HList.hs
@@ -0,0 +1,75 @@
+module Data.HList
+    ( HList
+    , HNil(..)
+    , hNil
+    , HCons(..)
+    , hCons
+
+    , HExtendable(..)
+    , HAppendable(..)
+
+    , (:*:)
+    , (.*.)
+    )
+    where
+
+import Data.Typeable
+
+-- HList
+class HList l
+
+-- HNil
+data HNil
+    = HNil
+      deriving (Show, Eq, Ord, Read, Typeable)
+
+instance HList HNil
+
+hNil :: HNil
+hNil = HNil
+
+-- HCons
+data HCons e l
+    = HCons e l
+      deriving (Show, Eq, Ord, Read, Typeable)
+
+instance HList l => HList (HCons e l)
+
+hCons :: HList l => e -> l -> HCons e l
+hCons = HCons
+
+-- HExtendable
+class HExtendable e l where
+    type HExtend e l
+    hExtend :: e -> l -> HExtend e l
+
+instance HExtendable e HNil where
+    type HExtend e HNil = HCons e HNil
+    hExtend e nil = hCons e nil
+
+instance HList l => HExtendable e (HCons e' l) where
+    type HExtend e (HCons e' l) = HCons e (HCons e' l)
+    hExtend e (HCons e' l) = hCons e (hCons e' l)
+
+-- HAppendable
+class HAppendable l l' where
+    type HAppend l l'
+    hAppend :: l -> l' -> HAppend l l'
+
+instance HList l => HAppendable HNil l where
+    type HAppend HNil l = l
+    hAppend _ l = l
+
+instance (HAppendable l l',
+          HList (HAppend l l')) => HAppendable (HCons e l) l' where
+    type HAppend (HCons e l) l' = HCons e (HAppend l l')
+    hAppend (HCons e l) l' = hCons e (hAppend l l')
+
+-- :*:
+infixr 2 :*:
+infixr 2 .*.
+
+type e :*: l = HCons e l
+
+(.*.) :: HExtendable e l => e -> l -> HExtend e l
+e .*. l = hExtend e l

diff --git a/Database/RRDtool.hs b/Database/RRDtool.hs
index 45ae91a3a36da7f675fca245a6de2c66abbcf07d..34867d0f19372ac2a80ec50a42feb1ae9944c086 100644 (file)
--- a/Database/RRDtool.hs
+++ b/Database/RRDtool.hs
@@ -1,6 +1,8 @@
 module Database.RRDtool
     ( DataSource(..)
 
+    , MentionedVars(..)
+
     , Expr
     , CommonExpr
     , IterativeExpr
@@ -10,7 +12,9 @@ module Database.RRDtool
     , CommonExprSet
 
     , Constant(..)
+    , VarName(..)
     , Variable(..)
+    , VariableSet
     , CommonUnaryOp(..)
     , CommonBinaryOp(..)
     , CommonTrinaryOp(..)
@@ -161,14 +165,15 @@ dsTest = COMPUTE {
            , dsExpr = AverageOf (Const 100 .*. Const 200 .*. HNil)
          }
 
+class VariableSet (MentionedVarsOf a) => MentionedVars a where
+    type MentionedVarsOf a
+
 class (Show e, Eq e) => Expr e
 class Expr e => CommonExpr e
 class Expr e => IterativeExpr e
 class Expr e => AggregativeExpr e
 instance CommonExpr e => IterativeExpr e
 
---class MentionedVars
-
 class (Show es, Eq es, HList es) => ExprSet es
 instance ExprSet HNil
 instance (Expr e, ExprSet es) => ExprSet (HCons e es)
@@ -185,12 +190,24 @@ data Constant
     deriving (Show, Eq, Ord)
 instance Expr Constant
 instance CommonExpr Constant
+instance MentionedVars Constant where
+    type MentionedVarsOf Constant = HNil
 
-class (Show a, Eq a) => Variable a where
+class (Show a, Eq a, Ord a) => VarName a where
     varName :: a -> String
 
-instance Variable a => Expr a
-instance Variable a => CommonExpr a
+data Variable vn
+    = Variable !vn
+    deriving (Show, Eq, Ord)
+
+instance VarName vn => Expr (Variable vn)
+instance VarName vn => CommonExpr (Variable vn)
+instance VarName vn => MentionedVars (Variable vn) where
+    type MentionedVarsOf (Variable vn) = vn :*: HNil
+
+class HList vs => VariableSet vs
+instance VariableSet HNil
+instance (VarName vn, VariableSet vs) => VariableSet (HCons vn vs)
 
 -- Common operators
 data CommonUnaryOp a
@@ -210,6 +227,8 @@ data CommonUnaryOp a
     deriving (Show, Eq, Ord)
 instance Expr a => Expr (CommonUnaryOp a)
 instance CommonExpr a => CommonExpr (CommonUnaryOp a)
+instance VariableSet (MentionedVarsOf a) => MentionedVars (CommonUnaryOp a) where
+    type MentionedVarsOf (CommonUnaryOp a) = MentionedVarsOf a
 
 data CommonBinaryOp a b
     = !a :<:  !b
@@ -228,10 +247,20 @@ data CommonBinaryOp a b
     | AddNaN !a !b
     | AtanXY !a !b
     deriving (Show, Eq, Ord)
-instance (Expr a, Expr b)
-    => Expr (CommonBinaryOp a b)
-instance (CommonExpr a, CommonExpr b)
-    => CommonExpr (CommonBinaryOp a b)
+
+instance (Expr a, Expr b) =>
+    Expr (CommonBinaryOp a b)
+
+instance (CommonExpr a, CommonExpr b) =>
+    CommonExpr (CommonBinaryOp a b)
+
+instance (VariableSet (MentionedVarsOf a),
+          VariableSet (MentionedVarsOf b),
+          VariableSet (HAppend (MentionedVarsOf a) (MentionedVarsOf b))) =>
+    MentionedVars (CommonBinaryOp a b) where
+        type MentionedVarsOf (CommonBinaryOp a b)
+            = HAppend (MentionedVarsOf a) (MentionedVarsOf b)
+        
 
 data CommonTrinaryOp a b c
     = If !a !b !c
@@ -251,30 +280,30 @@ data CommonSetOp es
 instance ExprSet es => Expr (CommonSetOp es)
 instance CommonExprSet es => CommonExpr (CommonSetOp es)
 
-data TrendOp v a
-    = Trend      !v !a
-    | TrendNan   !v !a
+data TrendOp vn a
+    = Trend      !(Variable vn) !a
+    | TrendNan   !(Variable vn) !a
     deriving (Show, Eq, Ord)
-instance (Variable v, Expr a) => Expr (TrendOp v a)
-instance (Variable v, CommonExpr a) => CommonExpr (TrendOp v a)
+instance (VarName vn, Expr a) => Expr (TrendOp vn a)
+instance (VarName vn, CommonExpr a) => CommonExpr (TrendOp vn a)
 
-data VariableShiftPredictOp ss w v
-    = VariableShiftPredictAverage !ss !w !v
-    | VariableShiftPredictSigma   !ss !w !v
+data VariableShiftPredictOp ss w vn
+    = VariableShiftPredictAverage !ss !w !(Variable vn)
+    | VariableShiftPredictSigma   !ss !w !(Variable vn)
     deriving (Show, Eq, Ord)
-instance (ExprSet ss, Expr w, Variable v)
-    => Expr (VariableShiftPredictOp ss w v)
-instance (CommonExprSet ss, CommonExpr w, Variable v)
-    => CommonExpr (VariableShiftPredictOp ss w v)
-
-data FixedShiftPredictOp sm w v
-    = FixedShiftPredictAverage !sm !w !v
-    | FixedShiftPredictSigma   !sm !w !v
+instance (ExprSet ss, Expr w, VarName vn)
+    => Expr (VariableShiftPredictOp ss w vn)
+instance (CommonExprSet ss, CommonExpr w, VarName vn)
+    => CommonExpr (VariableShiftPredictOp ss w vn)
+
+data FixedShiftPredictOp sm w vn
+    = FixedShiftPredictAverage !sm !w !(Variable vn)
+    | FixedShiftPredictSigma   !sm !w !(Variable vn)
     deriving (Show, Eq, Ord)
-instance (Expr sm, Expr w, Variable v)
-    => Expr (FixedShiftPredictOp sm w v)
-instance (CommonExpr sm, CommonExpr w, Variable v)
-    => CommonExpr (FixedShiftPredictOp sm w v)
+instance (Expr sm, Expr w, VarName vn)
+    => Expr (FixedShiftPredictOp sm w vn)
+instance (CommonExpr sm, CommonExpr w, VarName vn)
+    => CommonExpr (FixedShiftPredictOp sm w vn)
 
 -- Common special values
 data CommonValue
@@ -296,30 +325,30 @@ data IterativeValue
 instance Expr IterativeValue
 instance IterativeExpr IterativeValue
 
-data IterativeValueOf v
-    = PreviousOf !v
+data IterativeValueOf vn
+    = PreviousOf !(Variable vn)
     deriving (Show, Eq, Ord)
-instance Variable v => Expr (IterativeValueOf v)
-instance Variable v => IterativeExpr (IterativeValueOf v)
+instance VarName vn => Expr (IterativeValueOf vn)
+instance VarName vn => IterativeExpr (IterativeValueOf vn)
 
 -- Aggregative operators (fairly restricted due to rrdtool's
 -- restriction)
-data AggregativeUnaryOp v
-    = Maximum    !v
-    | Minimum    !v
-    | Average    !v
-    | StandardDeviation !v
-    | First      !v
-    | Last       !v
-    | Total      !v
-    | Percent    !v !Constant
-    | PercentNan !v !Constant
-    | LSLSlope   !v
-    | LSLInt     !v
-    | LSLCorrel  !v
+data AggregativeUnaryOp vn
+    = Maximum    !(Variable vn)
+    | Minimum    !(Variable vn)
+    | Average    !(Variable vn)
+    | StandardDeviation !(Variable vn)
+    | First      !(Variable vn)
+    | Last       !(Variable vn)
+    | Total      !(Variable vn)
+    | Percent    !(Variable vn) !Constant
+    | PercentNan !(Variable vn) !Constant
+    | LSLSlope   !(Variable vn)
+    | LSLInt     !(Variable vn)
+    | LSLCorrel  !(Variable vn)
     deriving (Show, Eq, Ord)
-instance Variable v => Expr (AggregativeUnaryOp v)
-instance Variable v => AggregativeExpr (AggregativeUnaryOp v)
+instance VarName vn => Expr (AggregativeUnaryOp vn)
+instance VarName vn => AggregativeExpr (AggregativeUnaryOp vn)
 
 -- |The 'createRRD' function lets you set up new Round Robin Database
 -- (RRD) files. The file is created at its final, full size and filled

diff --git a/rrdtool.cabal b/rrdtool.cabal
index 6dbb994ab584235ff55257ad588d982d12b5be92..880db9844573d5ab4cfe349cd06b21c60f70dd58 100644 (file)
--- a/rrdtool.cabal
+++ b/rrdtool.cabal
@@ -23,22 +23,26 @@ Source-Repository head
 
 Library
     Build-Depends:
-        HList           == 0.2.*,
         base            == 4.2.*,
         bindings-librrd == 0.1.*,
         time            == 1.1.*
 
     Extensions:
+        DeriveDataTypeable
         EmptyDataDecls
         ExistentialQuantification
+        FlexibleContexts
         FlexibleInstances
         IncoherentInstances
+        MultiParamTypeClasses
+        TypeFamilies
         TypeOperators
         TypeSynonymInstances
         UndecidableInstances
 
     Exposed-Modules:
         Database.RRDtool
+        Data.HList
 
     GHC-Options:
         -Wall
\ No newline at end of file