make variables a type class

diff --git a/Database/RRDtool.hs b/Database/RRDtool.hs
index f588fdb619686b5b5bd5efda0503e018356a63f2..45ae91a3a36da7f675fca245a6de2c66abbcf07d 100644 (file)
--- a/Database/RRDtool.hs
+++ b/Database/RRDtool.hs
@@ -15,10 +15,12 @@ module Database.RRDtool
     , CommonBinaryOp(..)
     , CommonTrinaryOp(..)
     , CommonSetOp(..)
+    , TrendOp(..)
     , VariableShiftPredictOp(..)
     , FixedShiftPredictOp(..)
     , CommonValue(..)
     , IterativeValue(..)
+    , IterativeValueOf(..)
     , AggregativeUnaryOp(..)
 
     , createRRD
@@ -165,6 +167,8 @@ 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)
@@ -182,11 +186,11 @@ data Constant
 instance Expr Constant
 instance CommonExpr Constant
 
-data Variable
-    = Var !String
-    deriving (Show, Eq, Ord)
-instance Expr Variable
-instance CommonExpr Variable
+class (Show a, Eq a) => Variable a where
+    varName :: a -> String
+
+instance Variable a => Expr a
+instance Variable a => CommonExpr a
 
 -- Common operators
 data CommonUnaryOp a
@@ -203,8 +207,6 @@ data CommonUnaryOp a
     | Deg2Rad    !a
     | Rad2Deg    !a
     | Abs        !a
-    | Trend      !Variable !a
-    | TrendNan   !Variable !a
     deriving (Show, Eq, Ord)
 instance Expr a => Expr (CommonUnaryOp a)
 instance CommonExpr a => CommonExpr (CommonUnaryOp a)
@@ -249,23 +251,30 @@ data CommonSetOp es
 instance ExprSet es => Expr (CommonSetOp es)
 instance CommonExprSet es => CommonExpr (CommonSetOp es)
 
-data VariableShiftPredictOp ss w
-    = VariableShiftPredictAverage !ss !w !Variable
-    | VariableShiftPredictSigma   !ss !w !Variable
+data TrendOp v a
+    = Trend      !v !a
+    | TrendNan   !v !a
     deriving (Show, Eq, Ord)
-instance (ExprSet ss, Expr w)
-    => Expr (VariableShiftPredictOp ss w)
-instance (CommonExprSet ss, CommonExpr w)
-    => CommonExpr (VariableShiftPredictOp ss w)
+instance (Variable v, Expr a) => Expr (TrendOp v a)
+instance (Variable v, CommonExpr a) => CommonExpr (TrendOp v a)
 
-data FixedShiftPredictOp sm w
-    = FixedShiftPredictAverage !sm !w !Variable
-    | FixedShiftPredictSigma   !sm !w !Variable
+data VariableShiftPredictOp ss w v
+    = VariableShiftPredictAverage !ss !w !v
+    | VariableShiftPredictSigma   !ss !w !v
     deriving (Show, Eq, Ord)
-instance (Expr sm, Expr w)
-    => Expr (FixedShiftPredictOp sm w)
-instance (CommonExpr sm, CommonExpr w)
-    => CommonExpr (FixedShiftPredictOp sm w)
+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
+    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)
 
 -- Common special values
 data CommonValue
@@ -280,7 +289,6 @@ instance CommonExpr CommonValue
 -- Iterative special values
 data IterativeValue
     = Previous
-    | PreviousOf !Variable
     | Count
     | TakenTime
     | TakenLocalTime
@@ -288,24 +296,30 @@ data IterativeValue
 instance Expr IterativeValue
 instance IterativeExpr IterativeValue
 
+data IterativeValueOf v
+    = PreviousOf !v
+    deriving (Show, Eq, Ord)
+instance Variable v => Expr (IterativeValueOf v)
+instance Variable v => IterativeExpr (IterativeValueOf v)
+
 -- Aggregative operators (fairly restricted due to rrdtool's
 -- restriction)
-data AggregativeUnaryOp
-    = Maximum    !Variable
-    | Minimum    !Variable
-    | Average    !Variable
-    | StandardDeviation !Variable
-    | First      !Variable
-    | Last       !Variable
-    | Total      !Variable
-    | Percent    !Variable !Constant
-    | PercentNan !Variable !Constant
-    | LSLSlope   !Variable
-    | LSLInt     !Variable
-    | LSLCorrel  !Variable
+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
     deriving (Show, Eq, Ord)
-instance Expr AggregativeUnaryOp
-instance AggregativeExpr AggregativeUnaryOp
+instance Variable v => Expr (AggregativeUnaryOp v)
+instance Variable v => AggregativeExpr (AggregativeUnaryOp v)
 
 -- |The 'createRRD' function lets you set up new Round Robin Database
 -- (RRD) files. The file is created at its final, full size and filled