{-# LANGUAGE GeneralizedNewtypeDeriving, DeriveDataTypeable #-} -- |The "Traced" module provides a simple way of tracing expression evaluation. -- A value of type @Traced a@ has both a value of type @a@ and an expression tree -- that describes how the value was computed. -- -- There are instances for the 'Traced' type for all numeric classes to make -- it simple to trace numeric expressions. -- -- The expression tree associated with a traced value is exactly that: a tree. -- But evaluation of expressions in Haskell typically has sharing to avoid recomputation. -- This sharing can be recovered by the (impure) 'reShare' function. -- -- $examples module Debug.Traced( Traced, traced, named, nameTraced, unknown, unTraced, tracedD, TracedD, unTracedD, Traceable, liftT, liftFun, Liftable, showAsExp, showAsExpFull, reShare, simplify, ifT, (%==), (%/=), (%<), (%<=), (%>), (%>=), (%&&), (%||), tnot, TracedExp, tracedExp, namedExp ) where import Data.Typeable(Typeable) import Debug.TracedInternal -- Boolean operations -- |Traced version of /if/. ifT :: (Traceable a) => Traced Bool -> Traced a -> Traced a -> Traced a ifT c t e = apply (unTraced $ if b then t else e) "ifT" Nonfix $ tracedD c : if b then [tracedD t, none] else [none, tracedD e] where none = tracedD u u = unknown "..." `asTypeOf` t b = unTraced c infix 4 %==, %/=, %<, %<=, %>, %>= -- |Comparisons generating traced booleans. (%==), (%/=) :: (Traceable a, Eq a) => Traced a -> Traced a -> Traced Bool (%==) = binOp (==) ("==", Infix 4) (%/=) = binOp (/=) ("/=", Infix 4) (%<), (%<=), (%>), (%>=) :: (Traceable a, Ord a) => Traced a -> Traced a -> Traced Bool (%<) = binOp (<) ("<", Infix 4) (%<=) = binOp (<=) ("<=", Infix 4) (%>) = binOp (>) (">", Infix 4) (%>=) = binOp (>=) (">=", Infix 4) infixr 3 %&& infixr 2 %|| (%&&) :: Traced Bool -> Traced Bool -> Traced Bool (%&&) = binOp (&&) ("&&", InfixR 3) (%||) :: Traced Bool -> Traced Bool -> Traced Bool (%||) = binOp (&&) ("||", InfixR 2) tnot :: Traced Bool -> Traced Bool tnot = unOp not "not" ----------------------------------- -- |A wrapper for 'Traced' to show it with full details. newtype TracedExp a = TracedExp (Traced a) deriving (Typeable, Eq, Ord, Num, Fractional, Integral, Enum, Real, RealFrac, Floating, RealFloat) instance (Traceable a, Show a) => Show (TracedExp a) where show (TracedExp x) = showAsExpFull x tracedExp :: (Traceable a) => a -> TracedExp a tracedExp = TracedExp . traced namedExp :: (Traceable a) => String -> a -> TracedExp a namedExp s = TracedExp . named s