{-# LANGUAGE CPP #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE OverloadedStrings #-} {-# LANGUAGE PatternGuards #-} {-# LANGUAGE TupleSections #-} {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE LambdaCase #-} -- | Generate presentations for types. module Present (-- * Presenting functions presentIt ,presentName ,presentType -- * Presentation mediums ,toShow ,toWHNF ,whnfJson -- * Debugging convenience functions ,presentShow -- * Types ,Value(..) ,WHNF(..) -- * Customization classes ,Present0(..) ,Present1(..) ,Present2(..) ,Present3(..) ,Present4(..) ,Present5(..) ,Present6(..)) where import Control.Arrow (second) import Control.Exception (evaluate,SomeException(..),try,evaluate) import Control.Monad (forM) import Control.Monad.Trans.State.Strict (evalStateT,get,modify,StateT(..)) import Data.Char (isSpace,ord,isAlphaNum) import Data.Int (Int8,Int16,Int32,Int64) import Data.List (nub,find,intercalate,foldl',isSuffixOf) import Data.Maybe (mapMaybe,isJust) import Data.Ratio (numerator,denominator) import Data.String (IsString) import Data.Typeable (typeOf) import Data.Word (Word8,Word32,Word64) import Foreign.ForeignPtr import Foreign.Ptr import Numeric (showHex) import System.IO.Unsafe (unsafePerformIO) import Text.Printf (printf) import qualified Language.Haskell.TH as TH import qualified Language.Haskell.TH.Syntax as TH -------------------------------------------------------------------------------- -- Introduction -- -- Present's algorithm works in stages/levels of work. The first -- implementation of Present worked, but was a mess. This -- implementation is an effort to separate all that functionality into -- clean, small stages. -------------------------------------------------------------------------------- -- Type Normalization -- -- TH's representation of types is wider than what Present cares -- about, and has some heterogeneity that is unwanted; it adds some -- messiness. To simplify the code further down, we perform this -- transformation to simplify the types and therefore the scope we -- have to deal with. -- -- TH's representation of names is also unfortunate, as it mixes up -- variables, types and type variables all together. We address that -- too. -- | A type variable. newtype TypeVariable = TypeVariable TH.Name deriving (Eq) -- | A type constructor. newtype TypeConstructor = TypeConstructor TH.Name deriving (Eq) -- | A primitive type constructor. newtype PrimitiveTypeConstructor = PrimitiveTypeConstructor TH.Name -- | A normalized type. data NormalType = NormalCons TypeConstructor | NormalPrimitive PrimitiveTypeConstructor | NormalFunction TH.Type | NormalVar TypeVariable | NormalApp NormalType [NormalType] -- | Convert the heterogenous TH type into a more normal form. normalizeType :: TH.Type -> Either String NormalType normalizeType = go where go = \case ty@TH.AppT{} -> do let (typeFunction,typeArguments) = flattenApplication ty case typeFunction of TH.ArrowT -> return (NormalFunction ty) _ -> NormalApp <$> go typeFunction <*> mapM go typeArguments TH.ForallT _ context ty -> if isFunction ty then return (NormalFunction ty) else go (typeClassDefaulting context ty) TH.SigT ty _kind -> go ty TH.VarT name -> return (NormalVar (TypeVariable name)) TH.ConT name -> return (if isPrimitiveType name then NormalPrimitive (PrimitiveTypeConstructor name) else NormalCons (TypeConstructor name)) TH.TupleT i -> case lookup i tupleConstructors of Nothing -> Left ("Tuple arity " ++ show i ++ " not supported.") Just cons -> return (NormalCons (TypeConstructor cons)) TH.ListT -> return (NormalCons (TypeConstructor ''[])) TH.PromotedT _ -> Left "Promoted types are not supported." TH.UnboxedTupleT _ -> Left "Unboxed tuples are not supported." TH.ArrowT -> Left "The function arrow (->) is not supported." TH.EqualityT -> Left "Equalities are not supported." TH.PromotedTupleT _ -> Left "Promoted types are not supported." TH.PromotedNilT -> Left "Promoted types are not supported." TH.PromotedConsT -> Left "Promoted types are not supported." TH.StarT -> Left "Star (*) is not supported." TH.ConstraintT -> Left "Constraints are not supported." TH.LitT _ -> Left "Type-level literals are not supported." #if MIN_VERSION_template_haskell(2,11,0) TH.InfixT{} -> Left "Infix type constructors are not supported." TH.UInfixT{} -> Left "Unresolved infix type constructors are not supported." TH.ParensT _ -> Left "Parenthesized types are not supported." TH.WildCardT -> Left "Wildcard types are not supported." #endif -- | Is the type a function? isFunction :: TH.Type -> Bool isFunction ty = let (typeFunction,_) = flattenApplication ty in case typeFunction of TH.ArrowT -> True _ -> False -- | Arity-constructor mapping for tuples. tupleConstructors :: [(Int,TH.Name)] tupleConstructors = [(0,''()) ,(2,''(,)) ,(3,''(,,)) ,(4,''(,,,)) ,(5,''(,,,,)) ,(6,''(,,,,,)) ,(7,''(,,,,,,)) ,(8,''(,,,,,,,)) ,(9,''(,,,,,,,,)) ,(10,''(,,,,,,,,,)) ,(11,''(,,,,,,,,,,)) ,(12,''(,,,,,,,,,,,)) ,(13,''(,,,,,,,,,,,,)) ,(14,''(,,,,,,,,,,,,,)) ,(15,''(,,,,,,,,,,,,,,)) ,(16,''(,,,,,,,,,,,,,,,)) ,(17,''(,,,,,,,,,,,,,,,,)) ,(18,''(,,,,,,,,,,,,,,,,,)) ,(19,''(,,,,,,,,,,,,,,,,,,)) ,(20,''(,,,,,,,,,,,,,,,,,,,)) ,(21,''(,,,,,,,,,,,,,,,,,,,,)) ,(22,''(,,,,,,,,,,,,,,,,,,,,,)) ,(23,''(,,,,,,,,,,,,,,,,,,,,,,)) ,(24,''(,,,,,,,,,,,,,,,,,,,,,,,)) ,(25,''(,,,,,,,,,,,,,,,,,,,,,,,,)) ,(26,''(,,,,,,,,,,,,,,,,,,,,,,,,,))] -- | Is the name specified by Name a primitive type? Like Int#? -- -- This check may be overly cautious, but it's also about as accurate -- as one can seemingly be. isPrimitiveType :: TH.Name -> Bool isPrimitiveType (TH.Name (TH.OccName _) (TH.NameG TH.TcClsName (TH.PkgName "ghc-prim") (TH.ModName "GHC.Prim"))) = True isPrimitiveType name = isSuffixOf "#" (show name) -- | Flatten a type application f x y into (f,[x,y]). flattenApplication :: TH.Type -> (TH.Type,[TH.Type]) flattenApplication = go [] where go args (TH.AppT f x) = go (x : args) f go args f = (f,args) -------------------------------------------------------------------------------- -- Defaulting -- -- For some classes like Num and IsString, we can default to a -- reasonable value in the REPL. It leads to a better user-experience. -- | Apply defaulted substitutions for each of the constraints in the -- type. typeClassDefaulting :: [TH.Type] -> TH.Type -> TH.Type typeClassDefaulting constraints = applyTypeSubstitution (mapMaybe (\case TH.AppT (TH.ConT className) (TH.VarT varName) -> fmap (\tyName -> (varName,TH.ConT tyName)) (lookup className defaultedClasses) _ -> Nothing) constraints) -- | Apply the given substitutions to the type. applyTypeSubstitution :: [(TH.Name,TH.Type)] -> TH.Type -> TH.Type applyTypeSubstitution subs = go where go = \case TH.ForallT vars ctx ty -> TH.ForallT vars ctx (go ty) TH.AppT f x -> TH.AppT (go f) (go x) TH.SigT ty k -> TH.SigT (go ty) k TH.VarT a | Just b <- lookup a subs -> b | otherwise -> TH.VarT a x -> x -- | Classes which when encountered in a forall context should have -- their corresponding type variables substituted on the right hand -- side with the given type. defaultedClasses :: [(TH.Name,TH.Name)] defaultedClasses = [(''Integral,''Integer) ,(''Num,''Integer) ,(''Fractional,''Double) ,(''Bounded,''()) ,(''Eq,''()) ,(''Read,''()) ,(''Show,''()) ,(''IsString,''String)] -------------------------------------------------------------------------------- -- Type Enumeration -- -- Given a NormalType, we extract all the instances of NormalCons into -- a flat set. -- -- We can then run through each type constructor name, reify them, and -- generate a printer for it. This separate step avoids cycles/acts as -- an alternative to performing an occurs check. -- | Enumerate all unique type constructors in the type. enumerateTypeConstructors :: NormalType -> [TypeConstructor] enumerateTypeConstructors = nub . go where go = \case NormalCons cons -> [cons] NormalApp ty tys -> go ty ++ concatMap go tys NormalPrimitive{} -> [] NormalVar{} -> [] NormalFunction{} -> [] -------------------------------------------------------------------------------- -- Type Reification -- -- We have to reify all the type constructors involved in a given -- type. -- -- | Name of a variable. newtype ValueVariable = ValueVariable TH.Name -- | Name of a value constructor. newtype ValueConstructor = ValueConstructor TH.Name -- | A normalize representation of a constructor. Present's main -- algorithm doesn't particularly care whether it's infix, a record, -- or whatever. data Constructor = Constructor {_constructorName :: ValueConstructor ,constructorFields :: [(Maybe ValueVariable,NormalType)]} -- | A data type. data DataType = DataType {_dataTypeVariables :: [TypeVariable] ,_dataTypeConstructors :: [Constructor]} -- | A type alias. data TypeAlias = TypeAlias {_aliasVariables :: [TypeVariable] ,_aliasType :: NormalType} -- | Definition of a type. data TypeDefinition = DataTypeDefinition TypeConstructor DataType | TypeAliasDefinition TypeConstructor TypeAlias -- | Reify all the constructors of a name. Unless it's primitive, in -- which case return nothing. reifyTypeDefinition :: TypeConstructor -> TH.Q (Maybe TypeDefinition) reifyTypeDefinition typeConstructor@(TypeConstructor name) = do info <- TH.reify name let result = case info of TH.TyConI dec -> case dec of #if MIN_VERSION_template_haskell(2,11,0) TH.DataD _cxt0 _ vars _mkind cons _cxt1 -> #else TH.DataD _cxt _ vars cons _deriving -> #endif do cs <- concat <$> mapM makeConstructors cons return (Just (DataTypeDefinition typeConstructor (DataType (map toTypeVariable vars) cs))) #if MIN_VERSION_template_haskell(2,11,0) TH.NewtypeD _cxt0 _ vars _mkind con _cxt1 -> #else TH.NewtypeD _cxt _ vars con _deriving -> #endif do cs <- makeConstructors con return (Just (DataTypeDefinition typeConstructor (DataType (map toTypeVariable vars) cs))) TH.TySynD _ vars ty -> do ty' <- normalizeType ty return (Just (TypeAliasDefinition typeConstructor (TypeAlias (map toTypeVariable vars) ty'))) _ -> Left "Not a supported data type declaration." TH.PrimTyConI{} -> return Nothing TH.FamilyI{} -> Left "Data families not supported yet." _ -> Left ("Not a supported object, no type inside it: " ++ TH.pprint info) case result of Left err -> fail err Right ok -> return ok -- | Convert a TH type variable to a normalized type variable. toTypeVariable :: TH.TyVarBndr -> TypeVariable toTypeVariable = \case TH.PlainTV t -> TypeVariable t TH.KindedTV t _ -> TypeVariable t -- | Make a normalized constructor from the more complex TH Con. makeConstructors :: TH.Con -> Either String [Constructor] makeConstructors = \case TH.NormalC name slots -> (:[]) <$> makeConstructor name (mapM makeSlot slots) TH.RecC name fields -> (:[]) <$> makeConstructor name (mapM makeField fields) TH.InfixC t1 name t2 -> (:[]) <$> makeConstructor name ((\x y -> [x,y]) <$> makeSlot t1 <*> makeSlot t2) (TH.ForallC _ _ con) -> makeConstructors con #if MIN_VERSION_template_haskell(2,11,0) TH.GadtC names slots _type -> forM names $ \name -> makeConstructor name (mapM makeSlot slots) TH.RecGadtC names fields _type -> forM names $ \name -> makeConstructor name (mapM makeField fields) #endif where makeConstructor name efields = Constructor (ValueConstructor name) <$> efields makeSlot (_,ty) = (Nothing,) <$> normalizeType ty makeField (name,_,ty) = (Just (ValueVariable name),) <$> normalizeType ty -------------------------------------------------------------------------------- -- Definition Elaboration -- -- When reifying a type, we discover that it refers to other types -- which in turn need to be reified. So to get the total of all types -- that we're going to want to generate a printer for, we need to -- recursively elaborate everything all the way down. -- -- A primitive type definition does not decompose into other types. -- | Elaborate the types involved in a type definition. definitionNormalTypes :: TypeDefinition -> [NormalType] definitionNormalTypes = \case DataTypeDefinition _ (DataType _ cons) -> concatMap (map snd . constructorFields) cons TypeAliasDefinition _ (TypeAlias _ ty) -> [ty] -------------------------------------------------------------------------------- -- Complete Expansion -- -- Finally, we need a way to, given a type, completely explode that -- type, and every type inside it, recursively, to produce a finite, -- unique set of TypeDefinitions. -- | Expand a type into all the type definitions directly or -- indirectly related. normalTypeDefinitions :: NormalType -> TH.Q [TypeDefinition] normalTypeDefinitions = flip evalStateT [] . expandNormalType where expandNormalType = fmap concat . mapM expandTypeConstructor . enumerateTypeConstructors expandTypeConstructor typeConstructor = do seenConstructors <- get if elem typeConstructor seenConstructors then return [] else do mtypeDefinition <- liftQ (reifyTypeDefinition typeConstructor) case mtypeDefinition of Nothing -> return [] Just typeDefinition -> do let normalTypes = definitionNormalTypes typeDefinition modify (typeConstructor :) typeDefinitions <- fmap concat (mapM expandNormalType normalTypes) return (typeDefinition : typeDefinitions) -- | Lift a Q monad into a StateT transformer. liftQ :: TH.Q a -> StateT s TH.Q a liftQ m = StateT (\s -> do v <- m return (v,s)) -------------------------------------------------------------------------------- -- Printer Generation -- -- Given a TypeDefinition, generate a printer for that data type. data Value = DataValue String String [Value] | TypeVariableValue String | PrimitiveValue String | FunctionValue String | CharValue String String | IntegerValue String String | ChoiceValue String [(String,Value)] | RecordValue String String [(String,Value)] | ListValue String [Value] | StringValue String String | TupleValue String [Value] | ExceptionValue String String deriving (Show) -- | Make a presenter for a type definition. typeDefinitionPresenter :: [(TypeConstructor,ValueVariable)] -> TypeDefinition -> TH.Q [TH.Dec] typeDefinitionPresenter instances = \case DataTypeDefinition typeConstructor dataType@(DataType typeVariables _) -> case find (namesBasicallyEqual typeConstructor . fst) instances of Nothing -> case find (namesBasicallyEqual typeConstructor . fst) builtInPresenters of Nothing -> dataTypePresenter typeConstructor dataType Just (_,presenter) -> do automaticPresenter <- dataTypePresenterBody typeConstructor dataType builtinFunctionDeclaration typeConstructor (presenter typeVariables automaticPresenter) Just (_,methodName) -> do instanceBasedPresenter typeConstructor methodName dataType typeVariables TypeAliasDefinition typeConstructor typeAlias -> typeAliasPresenter typeConstructor typeAlias -- | Make a printer based on an instance declaration for Present[N]. instanceBasedPresenter :: TypeConstructor -> ValueVariable -> DataType -> [TypeVariable] -> TH.Q [TH.Dec] instanceBasedPresenter typeConstructor@(TypeConstructor typeConstructorName) (ValueVariable methodName) dataType typeVariables = presentingFunctionDeclaration typeConstructor typeVariables (TH.tupE [typeDisplayExpression ,[|\x -> ChoiceValue $(typeDisplayExpression) [("Instance" ,snd $(foldl TH.appE (TH.varE methodName) (map (TH.varE . presentVarName) typeVariables)) x) ,("Internal" ,$(dataTypePresenterBody typeConstructor dataType) x)]|]]) where typeDisplayExpression = typeDisplay typeVariables typeConstructorName -- | Make a presenter for the given data type. dataTypePresenter :: TypeConstructor -> DataType -> TH.Q [TH.Dec] dataTypePresenter typeConstructor@(TypeConstructor typeConstructorName) dataType@(DataType typeVariables _) = presentingFunctionDeclaration typeConstructor typeVariables (TH.tupE [typeDisplayExpression ,dataTypePresenterBody typeConstructor dataType]) where typeDisplayExpression = typeDisplay typeVariables typeConstructorName -- | Make a printer for a data type, just the expression part. dataTypePresenterBody :: TypeConstructor -> DataType -> TH.Q TH.Exp dataTypePresenterBody (TypeConstructor typeConstructorName) (DataType typeVariables constructors) = TH.lamCaseE (map constructorCase constructors) where typeDisplayExpression = typeDisplay typeVariables typeConstructorName constructorCase (Constructor (ValueConstructor valueConstructorName) fields) = TH.match (TH.conP valueConstructorName (map (return . fieldPattern) indexedFields)) (TH.normalB (TH.appE presentationConstructor (TH.listE (map fieldPresenter indexedFields)))) [] where presentationConstructor = if isTuple typeConstructorName then TH.appE (TH.conE 'TupleValue) typeDisplayExpression else TH.appE (TH.appE (TH.conE (if any (isJust . fst) fields && not (null fields) then 'RecordValue else 'DataValue)) typeDisplayExpression) (TH.litE (TH.stringL (TH.pprint valueConstructorName))) indexedFields = zip (map indexedFieldName [0 ..]) fields fieldPattern (indexedName,_) = TH.VarP indexedName fieldPresenter (indexedName,(mvalueVariable,normalType)) = addField (TH.appE (TH.appE (TH.varE 'snd) (expressType typeVariables normalType)) (TH.varE indexedName)) where addField = case mvalueVariable of Nothing -> id Just (ValueVariable fieldName) -> \e -> TH.tupE [TH.stringE (TH.pprint fieldName),e] -- | Generate an expression which displays a data type and its -- type variables as instantiated. typeDisplay :: [TypeVariable] -> TH.Name -> TH.Q TH.Exp typeDisplay typeVariables name = (applyToVars . TH.litE . TH.stringL . TH.pprint) name where applyToVars typeConstructorDisplay | null typeVariables = typeConstructorDisplay | isTuple name = [|("(" ++ intercalate "," $(TH.listE (map (\typeVariable -> TH.appE (TH.varE 'fst) (TH.varE (presentVarName typeVariable))) typeVariables)) ++ ")")|] | otherwise = TH.appE (TH.varE 'unwords) (TH.infixE (Just (TH.listE [typeConstructorDisplay])) (TH.varE '(++)) (Just (TH.listE (map (\typeVariable -> TH.appE (TH.varE 'parensIfNeeded) (TH.appE (TH.varE 'fst) (TH.varE (presentVarName typeVariable)))) typeVariables)))) -- | Is a name a tuple? isTuple :: TH.Name -> Bool isTuple typeConstructorName = any ((== typeConstructorName) . snd) tupleConstructors -- | Add parens to a string if there's a space inside. parensIfNeeded :: [Char] -> [Char] parensIfNeeded e = if any isSpace e then "(" ++ e ++ ")" else e -- | Make a name for an indexed field of a data type constructor. indexedFieldName :: Integer -> TH.Name indexedFieldName index = TH.mkName ("indexedField_" ++ show index) -- | Make a printer for a type-alias. This involves simply proxying to -- the real printer, whether that's a data type or a primitive, or -- another type-alias. typeAliasPresenter :: TypeConstructor -> TypeAlias -> TH.Q [TH.Dec] typeAliasPresenter typeConstructor@(TypeConstructor typeConstructorName) (TypeAlias typeVariables normalType) = presentingFunctionDeclaration typeConstructor typeVariables (TH.tupE [TH.litE (TH.stringL (TH.pprint typeConstructorName)) ,TH.appE (TH.varE 'snd) (expressType typeVariables normalType)]) -- | Make a presenting function. builtinFunctionDeclaration :: TypeConstructor -> TH.Q TH.Exp -> TH.Q [TH.Dec] builtinFunctionDeclaration typeConstructor body = do dec <- TH.valD (TH.varP name) (TH.normalB body) [] return [dec] where name = presentConsName typeConstructor -- | Make a presenting function. presentingFunctionDeclaration :: TypeConstructor -> [TypeVariable] -> TH.Q TH.Exp -> TH.Q [TH.Dec] presentingFunctionDeclaration typeConstructor@(TypeConstructor typeConstructorName) typeVariables body = do sig <- TH.sigD name (TH.forallT (map (\(TypeVariable typeVariable) -> TH.PlainTV typeVariable) typeVariables) (return []) (foldl (\inner (TypeVariable typeVariable) -> let presentTypeVariable = return (TH.AppT (TH.AppT (TH.TupleT 2) (TH.ConT ''String)) presenter) where presenter = TH.AppT (TH.AppT TH.ArrowT (TH.VarT typeVariable)) (TH.ConT ''Value) in TH.appT (TH.appT TH.arrowT presentTypeVariable) inner) tupleType (reverse typeVariables))) dec <- if null typeVariables then TH.valD (TH.varP name) (TH.normalB body) [] else TH.funD name [TH.clause (map (\typeVariable -> TH.varP (presentVarName typeVariable)) typeVariables) (TH.normalB body) []] return [sig,dec] where name = presentConsName typeConstructor tupleType = ((\string typ -> TH.AppT (TH.AppT (TH.TupleT 2) string) typ) <$> TH.conT ''String <*> TH.appT (TH.appT TH.arrowT appliedType) (TH.conT ''Value)) appliedType = foldl TH.appT (TH.conT typeConstructorName) (map (\(TypeVariable typeVariableName) -> TH.varT typeVariableName) typeVariables) -------------------------------------------------------------------------------- -- Built-in printers -- | Are the names basically equal, disregarding package id buggerances? namesBasicallyEqual :: TypeConstructor -> TypeConstructor -> Bool namesBasicallyEqual (TypeConstructor this) (TypeConstructor that) = normalize this == normalize that where normalize n@(TH.Name name flavour) = case flavour of TH.NameG _ _ modName -> TH.Name name (TH.NameQ modName) _ -> n -- | Printers for built-in data types with custom representations -- (think: primitives, tuples, etc.) builtInPresenters :: [(TypeConstructor,[TypeVariable] -> TH.Exp -> TH.Q TH.Exp)] builtInPresenters = concat [listPrinters ,integerPrinters ,realPrinters ,charPrinters ,packedStrings ,vectorPrinters ,pointerPrinters] -- | Vectors. vectorPrinters :: [(TypeConstructor,[TypeVariable] -> TH.Exp -> TH.Q TH.Exp)] vectorPrinters = [makeVectorPrinter (qualified "Data.Vector" "Vector") (qualified "Data.Vector" "toList")] where makeVectorPrinter typeName unpackFunction = (TypeConstructor typeName ,\(typeVariable:_) automaticPrinter -> (let presentVar = TH.varE (presentVarName typeVariable) in TH.lamE [TH.varP (presentVarName typeVariable)] [|(let typeString = $(TH.stringE (TH.pprint typeName)) ++ " " ++ parensIfNeeded (fst $(presentVar)) in (typeString ,\xs -> ChoiceValue typeString [("List" ,ListValue typeString (map (snd $(presentVar)) ($(TH.varE unpackFunction) xs))) ,("Internal",$(return automaticPrinter) xs)]))|])) qualified modName term = TH.Name (TH.OccName term) (TH.NameQ (TH.ModName modName)) -- | Packed strings; Text, ByteString. -- -- This function cleverly acccess functions from these packages in the -- code generation, without actually needing the `present' package to -- depend on them directly. -- packedStrings :: [(TypeConstructor,a -> TH.Exp -> TH.Q TH.Exp)] packedStrings = [makeStringPrinter (qualified "Data.ByteString.Internal" "ByteString") (qualified "Data.ByteString.Char8" "unpack") ,makeStringPrinter (qualified "Data.ByteString.Lazy.Internal" "ByteString") (qualified "Data.ByteString.Lazy.Char8" "unpack") ,makeStringPrinter (qualified "Data.Text.Internal" "Text") (qualified "Data.Text" "unpack") ,makeStringPrinter (qualified "Data.Text.Internal.Lazy" "Text") (qualified "Data.Text.Lazy" "unpack")] where makeStringPrinter typeName unpackFunction = (TypeConstructor typeName ,\_ internal -> [|let typeString = $(TH.stringE (TH.pprint typeName)) in (typeString ,\xs -> ChoiceValue typeString [("String" ,StringValue typeString ($(TH.varE unpackFunction) xs)) ,("Internal",$(return internal) xs)])|]) qualified modName term = TH.Name (TH.OccName term) (TH.NameQ (TH.ModName modName)) -- | Printers for list-like types. listPrinters :: [(TypeConstructor,[TypeVariable] -> TH.Exp -> TH.Q TH.Exp)] listPrinters = [(TypeConstructor ''[] ,\(typeVariable:_) _automaticPrinter -> (let presentVar = TH.varE (presentVarName typeVariable) in TH.lamE [TH.varP (presentVarName typeVariable)] [|(let typeString = "[" ++ fst $(presentVar) ++ "]" in (typeString ,\xs -> ListValue typeString (map (snd $(presentVar)) xs)))|]))] -- | Printers for character-like types. charPrinters :: [(TypeConstructor,a -> TH.Exp -> TH.Q TH.Exp)] charPrinters = map makeCharPrinter [''Char] where makeCharPrinter name = (TypeConstructor name ,\_ automaticPrinter -> [|($(TH.stringE (show name)) ,\c -> ChoiceValue $(TH.stringE (show name)) [("Character" ,CharValue $(TH.stringE (show name)) (return c)) ,("Unicode point",($(intPrinter Nothing name) (ord c))) ,("Internal",$(return automaticPrinter) c)])|]) -- | Printers for pointer types. pointerPrinters :: [(TypeConstructor,[TypeVariable] -> TH.Exp -> TH.Q TH.Exp)] pointerPrinters = map makePtrPrinter [''Ptr,''ForeignPtr,''FunPtr] where makePtrPrinter name = (TypeConstructor name ,\(typeVariable:_) automaticPrinter -> (let presentVar = TH.varE (presentVarName typeVariable) in TH.lamE [TH.varP (presentVarName typeVariable)] [|(let typeString = $(TH.stringE (show name)) ++ " " ++ parensIfNeeded (fst $(presentVar)) in (typeString ,\x -> ChoiceValue typeString [("Pointer" ,IntegerValue typeString (show x)) ,("Internal",$(return automaticPrinter) x)]))|])) -- | Printers for real number types. realPrinters :: [(TypeConstructor,a -> TH.Exp -> TH.Q TH.Exp)] realPrinters = map makeIntPrinter [''Float,''Double] where makeIntPrinter name = (TypeConstructor name ,\_ automaticPrinter -> [|($(TH.stringE (show name)) ,$(floatingPrinter (Just automaticPrinter) name))|]) -- | Printers for integral types. integerPrinters :: [(TypeConstructor,a -> TH.Exp -> TH.Q TH.Exp)] integerPrinters = map makeIntPrinter [''Integer ,''Int ,''Int8 ,''Int16 ,''Int32 ,''Int64 ,''Word ,''Word8 ,''Word32 ,''Word64] where makeIntPrinter name = (TypeConstructor name ,\_ automaticPrinter -> [|($(TH.stringE (show name)) ,$(intPrinter (Just automaticPrinter) name))|]) -- | Show a rational as x/y. showRational :: Rational -> String showRational x = show (numerator x) ++ "/" ++ show (denominator x) -- | Floating point printer. floatingPrinter :: Maybe TH.Exp -> TH.Name -> TH.Q TH.Exp floatingPrinter mautomaticPrinter name = [|\x -> ChoiceValue $(TH.stringE (show name)) $(case mautomaticPrinter of Nothing -> [|[("Floating" ,IntegerValue $(TH.stringE (show name)) (printf "%f" x)) ,("Show" ,IntegerValue $(TH.stringE (show name)) (show x)) ,("Rational" ,IntegerValue $(TH.stringE (show name)) (showRational (toRational x)))]|] Just automaticPrinter -> [|[("Floating" ,IntegerValue $(TH.stringE (show name)) (printf "%f" x)) ,("Show" ,IntegerValue $(TH.stringE (show name)) (show x)) ,("Rational" ,IntegerValue $(TH.stringE (show name)) (showRational (toRational x))) ,("Internal",$(return automaticPrinter) x)]|])|] -- | Integer printer. intPrinter :: Maybe TH.Exp -> TH.Name -> TH.Q TH.Exp intPrinter mautomaticPrinter name = [|\x -> ChoiceValue $(TH.stringE (show name)) $(case mautomaticPrinter of Nothing -> [|[("Decimal" ,IntegerValue $(TH.stringE (show name)) (show x)) ,("Hexadecimal" ,IntegerValue $(TH.stringE (show name)) (Text.Printf.printf "%x" x)) ,("Binary" ,IntegerValue $(TH.stringE (show name)) (Text.Printf.printf "%b" x))]|] Just automaticPrinter -> [|[("Decimal" ,IntegerValue $(TH.stringE (show name)) (show x)) ,("Hexadecimal" ,IntegerValue $(TH.stringE (show name)) (Text.Printf.printf "%x" x)) ,("Binary" ,IntegerValue $(TH.stringE (show name)) (Text.Printf.printf "%b" x)) ,("Internal",$(return automaticPrinter) x)]|])|] -------------------------------------------------------------------------------- -- Type Expression -- -- Given a type, we generate an expression capable of printing that -- type. It's just a simple translation from type application to -- function application. -- -- | Make an expression for presenting a type. This doesn't actually -- do any unpacking of the data structures pertaining to the types, -- but rather makes calls to the functions that do. expressType :: [TypeVariable] -> NormalType -> TH.Q TH.Exp expressType = go 0 where go arity typeVariables = \case NormalVar ty -> if elem ty typeVariables then TH.varE (presentVarName ty) else return (presentUnknownVar ty arity) NormalCons cons -> TH.varE (presentConsName cons) NormalPrimitive (PrimitiveTypeConstructor typeConstructorName) -> expressPrimitive typeConstructorName NormalFunction ty -> return (TH.TupE [TH.LitE (TH.StringL (TH.pprint ty)) ,TH.LamE [TH.WildP] (TH.AppE (TH.ConE 'FunctionValue) (TH.LitE (TH.StringL (TH.pprint ty))))]) NormalApp f args -> foldl TH.appE (go (length args) typeVariables f) (map (go 0 typeVariables) args) -- | Express a primitive printer. expressPrimitive :: TH.Name -> TH.Q TH.Exp expressPrimitive typeConstructorName = do info <- TH.reify typeConstructorName case info of TH.PrimTyConI _ arity _unlifted -> return (ignoreTypeVariables arity (TH.TupE [TH.LitE (TH.StringL (TH.pprint typeConstructorName)) ,TH.LamE [TH.WildP] (TH.AppE (TH.ConE 'PrimitiveValue) (TH.LitE (TH.StringL (TH.pprint typeConstructorName))))])) _ -> fail ("Mistaken primitive type: " ++ TH.pprint typeConstructorName) -- | Name for a function name for presenting a type variable of a data -- type. presentUnknownVar :: TypeVariable -> Int -> TH.Exp presentUnknownVar (TypeVariable ty) arity = ignoreTypeVariables arity (TH.TupE [TH.LitE (TH.StringL (TH.pprint ty)) ,TH.LamE [TH.WildP] (TH.AppE (TH.ConE 'TypeVariableValue) (TH.LitE (TH.StringL (TH.pprint ty))))]) -- | Given the arity, make a lambda of that arity and ignore all the -- paramters. ignoreTypeVariables :: Int -> TH.Exp -> TH.Exp ignoreTypeVariables arity | arity == 0 = id | otherwise = TH.ParensE . TH.LamE (replicate arity TH.WildP) -- | Name for a function name for presenting a type variable of a data -- type. presentVarName :: TypeVariable -> TH.Name presentVarName (TypeVariable ty) = TH.mkName ("presentVar_" ++ normalizeName ty) -- | Name for a function name for presenting a type constructor. presentConsName :: TypeConstructor -> TH.Name presentConsName (TypeConstructor ty) = TH.mkName ("presentCons_" ++ normalizeName ty) -- | Normalize a name into a regular format. normalizeName :: TH.Name -> String normalizeName x = concatMap replace (show x) where replace 'z' = "zz" replace c | isAlphaNum c = [c] | otherwise = "z" ++ printf "%x" (ord c) -------------------------------------------------------------------------------- -- Extension classes -- -- Some user-defined data structures might have some specific opaque -- representations, so having some extension classes for a few of them -- allows us to provide altnerative representations. If such instances -- are provided, they will be prefered above the other default -- printers. -- | Get a mapping from type to instance methods of instances of -- Present, Present1, etc. getPresentInstances :: TH.Q [(TypeConstructor,ValueVariable)] getPresentInstances = do p0 <- getFor ''Present0 p1 <- getFor ''Present1 p2 <- getFor ''Present2 p3 <- getFor ''Present3 p4 <- getFor ''Present4 return (concat [p0,p1,p2,p3,p4]) where getFor cls = do result <- TH.reify cls case result of TH.ClassI (TH.ClassD _ _ _ _ [TH.SigD method _]) instances -> return (mapMaybe (\i -> case i of #if MIN_VERSION_template_haskell(2,11,0) TH.InstanceD _moverlap _ (TH.AppT (TH.ConT _className) (TH.ConT typeName)) _ -> #else TH.InstanceD _ (TH.AppT (TH.ConT _className) (TH.ConT typeName)) _ -> #endif Just (TypeConstructor typeName ,ValueVariable method) _ -> Nothing) instances) _ -> return [] class Present0 a where present0 :: (String,a -> Value) class Present1 a where present1 :: (String,x -> Value) -> (String,a x -> Value) class Present2 a where present2 :: (String,x -> Value) -> (String,y -> Value) -> (String,a x y -> Value) class Present3 a where present3 :: (String,x -> Value) -> (String,y -> Value) -> (String,z -> Value) -> (String,a x y z -> Value) class Present4 a where present4 :: (String,x -> Value) -> (String,y -> Value) -> (String,z -> Value) -> (String,z0 -> Value) -> (String,a x y z z0 -> Value) class Present5 a where present5 :: (String,x -> Value) -> (String,y -> Value) -> (String,z -> Value) -> (String,z0 -> Value) -> (String,z1 -> Value) -> (String,a x y z z0 z1 -> Value) class Present6 a where present6 :: (String,x -> Value) -> (String,y -> Value) -> (String,z -> Value) -> (String,z0 -> Value) -> (String,z1 -> Value) -> (String,z2 -> Value) -> (String,a x y z z0 z1 z2 -> Value) -------------------------------------------------------------------------------- -- Actual Presenting -- -- Finally, we take the type of `it' and generate a set of presenters -- for it and present the value in a self-contained let-expression. -- | Present whatever in scope is called `it' presentIt :: TH.Q TH.Exp presentIt = presentName (TH.mkName "it") -- | Make a presenter for the name presentName :: TH.Name -> TH.Q TH.Exp presentName name = do result <- tryQ (TH.reify name) case result of Nothing -> fail "Name `it' isn't in scope." #if MIN_VERSION_template_haskell(2,11,0) Just (TH.VarI _ ty _) -> #else Just (TH.VarI _ ty _ _) -> #endif TH.appE (presentType (return ty)) (TH.varE name) _ -> fail "The name `it' isn't a variable." where tryQ m = TH.recover (pure Nothing) (fmap Just m) -- | Present the value with the given type. presentType :: TH.Q TH.Type -> TH.Q TH.Exp presentType getTy = do ty <- getTy let normalizeResult = normalizeType ty case normalizeResult of Left err -> fail err Right normalType -> do instances <- getPresentInstances typeDefinitions <- normalTypeDefinitions normalType presenters <- mapM (typeDefinitionPresenter instances) typeDefinitions TH.letE (map return (concat presenters)) (TH.infixE (Just (TH.varE 'wrapExceptions)) (TH.varE '(.)) (Just (TH.appE (TH.varE 'snd) (expressType [] normalType)))) -------------------------------------------------------------------------------- -- Debugging helpers -- | Present a value and then use 'toShow' on it. -- -- >>> :t $(presentShow [t|Maybe Int|]) -- $(presentShow [t|Maybe Int|]) :: Maybe Int -> String presentShow :: TH.Q TH.Type -> TH.Q TH.Exp presentShow ty = [|toShow False . $(presentType ty)|] -------------------------------------------------------------------------------- -- Exception handling -- -- We want to be able to handle exceptions ("bottom") in data -- structures, which is particular to Haskell, by returning that as a -- presentation, too. So instead of failing to present a data -- structure just because it has _|_ in it, let's instead put an -- ExceptionValue inside it that can be presented to the user -- in a sensible manner. -- | Wrap any _|_ in the presentation with an exception handler. wrapExceptions :: Value -> Value wrapExceptions = wrap . go where wrap = either (\(SomeException exception) -> ExceptionValue (show (typeOf exception)) (show exception)) id . trySpoon go = \case DataValue a b ps -> DataValue a b (map wrapExceptions ps) ChoiceValue ty lps -> ChoiceValue ty (map (second wrapExceptions) lps) RecordValue ty c lps -> RecordValue ty c (map (second wrapExceptions) lps) ListValue ty ps -> seq ps (ListValue ty (map wrapExceptions ps)) TupleValue ty ps -> seq ps (TupleValue ty (map wrapExceptions ps)) p@(CharValue _ x) -> seqString p x p@(IntegerValue _ x) -> seqString p x p@TypeVariableValue{} -> p p@PrimitiveValue{} -> p p@FunctionValue{} -> p p@(StringValue _ x) -> seqString p x p@ExceptionValue{} -> p -- | Seq a string. seqString :: Value -> String -> Value seqString = foldl' (\presentation x -> seq x presentation) -- | Try to get a non-bottom value from the @a@, otherwise return the -- exception. trySpoon :: a -> Either SomeException a trySpoon a = unsafePerformIO (try (evaluate a)) -------------------------------------------------------------------------------- -- Value mediums -- -- A presentation by itself is useless, it has to be presented in a -- medium. -- | To a familiar Show-like string. toShow :: Bool -> Value -> String toShow qualified = \case IntegerValue _ i -> i ExceptionValue ex display -> "<" ++ ex ++ ": " ++ show display ++ ">" TypeVariableValue ty -> "<_ :: " ++ ty ++ ">" CharValue _ c -> "'" ++ c ++ "'" FunctionValue ty -> "<" ++ unwords (lines ty) ++ ">" DataValue _type name slots -> qualify name ++ (if null slots then "" else " ") ++ intercalate " " (map recur slots) RecordValue _type name fields -> qualify name ++ " {" ++ intercalate "," (map showField fields) ++ "}" where showField (fname,slot) = qualify fname ++ " = " ++ toShow qualified slot TupleValue _type slots -> "(" ++ intercalate "," (map (toShow qualified) slots) ++ ")" ListValue typ slots -> if typ == "[GHC.Types.Char]" then show (concatMap (\case CharValue _ c -> c ChoiceValue _ ((_,CharValue _ c):_) -> c _ -> []) slots) else "[" ++ intercalate "," (map (toShow qualified) slots) ++ "]" PrimitiveValue p -> "<" ++ p ++ ">" StringValue _ string -> show string ChoiceValue ty ((_,x):choices) -> case x of ExceptionValue{} | not (null choices) -> toShow qualified (ChoiceValue ty choices) _ -> toShow qualified x ChoiceValue _ [] -> "" where recur p | atomic p = toShow qualified p | otherwise = "(" ++ toShow qualified p ++ ")" where atomic = \case ListValue{} -> True IntegerValue{} -> True CharValue{} -> True StringValue{} -> True ChoiceValue ty ((_,x):xs) -> case x of ExceptionValue{} | not (null xs) -> atomic (ChoiceValue ty xs) _ -> atomic x DataValue _ _ [] -> True PrimitiveValue _ -> True _ -> False qualify x = if qualified then x else reverse (takeWhile (/= '.') (reverse x)) -- | A presentation of a value up to WHNF. data WHNF = DataWHNF String String [(String,[Integer])] | TypeVariableWHNF String | PrimitiveWHNF String | FunctionWHNF String | CharWHNF String String | IntegerWHNF String String | ChoiceWHNF String [(String,[Integer])] | RecordWHNF String String [(String,String,[Integer])] | ListConsWHNF String [Integer] [Integer] | ListEndWHNF String | StringWHNF String String | TupleWHNF String [(String,[Integer])] | ExceptionWHNF String String deriving (Show) -- | Produce a presentation of the value to WHNF. toWHNF :: [Integer] -- ^ Cursor. -> Value -- ^ Value to cursor into. -> WHNF -- ^ A WHNF presentation of the value at @cursor@. toWHNF = go [] where go :: [Integer] -> [Integer] -> Value -> WHNF go stack cursor = \case DataValue typ name slots -> case cursor of (slot:subCursor) -> case lookup slot (zip [0 ..] slots) of Nothing -> error "toWHNF: Invalid slot." Just value -> go (push [slot]) subCursor value _ -> DataWHNF typ name (zipWith (\index slot -> (valueType slot,push (cursor ++ [index]))) [0 ..] slots) ChoiceValue ty slots -> case cursor of (slot:subCursor) -> case lookup slot (zip [0 ..] slots) of Nothing -> error "toWHNF: Invalid slot." Just (_,value) -> go (push [slot]) subCursor value _ -> ChoiceWHNF ty (zipWith (\index (string,_) -> (string,push (cursor ++ [index]))) [0 ..] slots) RecordValue typ name slots -> case cursor of (slot:subCursor) -> case lookup slot (zip [0 ..] slots) of Nothing -> error "toWHNF: Invalid slot." Just (_,value) -> go (push [slot]) subCursor value _ -> RecordWHNF typ name (zipWith (\index (fname,slot) -> (valueType slot,fname,push (cursor ++ [index]))) [0 ..] slots) ListValue ty slots -> case cursor of (slot:subCursor) -> case slot of 0 -> case slots of (value0:_) -> go (push [slot]) subCursor value0 _ -> ListEndWHNF ty _ -> case slots of (_:value1) -> go (push [slot]) subCursor (ListValue ty value1) _ -> ListEndWHNF ty _ -> case slots of [] -> ListEndWHNF ty (_:_) -> ListConsWHNF ty (push cursor ++ [0]) (push cursor ++ [1]) TupleValue ty slots -> case cursor of (slot:subCursor) -> case lookup slot (zip [0 ..] slots) of Nothing -> error "toWHNF: Invalid slot." Just value -> go (push [slot]) subCursor value _ -> TupleWHNF ty (zipWith (\index slot -> (valueType slot ,push (cursor ++ [index]))) [0 ..] slots) TypeVariableValue ty -> TypeVariableWHNF ty PrimitiveValue ty -> PrimitiveWHNF ty FunctionValue ty -> FunctionWHNF ty CharValue ty ch -> CharWHNF ty ch IntegerValue ty rep -> IntegerWHNF ty rep StringValue ty str -> StringWHNF ty str ExceptionValue ty c -> ExceptionWHNF ty c where push xs = stack ++ xs -- | Get the type of a value. valueType :: Value -> String valueType = \case DataValue ty _ _ -> ty TypeVariableValue ty -> ty PrimitiveValue ty -> ty FunctionValue ty -> ty CharValue ty _ -> ty IntegerValue ty _ -> ty ChoiceValue ty _ -> ty RecordValue ty _ _ -> ty ListValue ty _ -> ty StringValue ty _ -> ty TupleValue ty _ -> ty ExceptionValue ty _ -> ty -- | Make JSON from WNHF. whnfJson :: WHNF -> String whnfJson = \case DataWHNF ty name slots -> jsonObject [("constructor",jsonString "data") ,("type",jsonString ty) ,("name",jsonString name) ,("slots" ,jsonList (map (\(typ,sid) -> jsonObject [("type",jsonString typ) ,("id",jsonList (map jsonInteger sid))]) slots))] TypeVariableWHNF var -> jsonObject [("constructor",jsonString "type-variable"),("type",jsonString var)] PrimitiveWHNF name -> jsonObject [("constructor",jsonString "primitive"),("type",jsonString name)] FunctionWHNF ty -> jsonObject [("constructor",jsonString "primitive"),("type",jsonString ty)] CharWHNF ty string -> jsonObject [("constructor",jsonString "char") ,("type",jsonString ty) ,("string",jsonString string)] IntegerWHNF ty string -> jsonObject [("constructor",jsonString "integer") ,("type",jsonString ty) ,("string",jsonString string)] ChoiceWHNF ty slots -> jsonObject [("constructor",jsonString "choice") ,("type",jsonString ty) ,("slots" ,jsonList (map (\(typ,sid) -> jsonObject [("title",jsonString typ) ,("id",jsonList (map jsonInteger sid))]) slots))] RecordWHNF ty name slots -> jsonObject [("constructor",jsonString "record") ,("type",jsonString ty) ,("name",jsonString name) ,("slots" ,jsonList (map (\(typ,name',sid) -> jsonObject [("type",jsonString typ) ,("name",jsonString name') ,("id",jsonList (map jsonInteger sid))]) slots))] ListConsWHNF typ x xs -> jsonObject [("constructor",jsonString "list-cons") ,("type",jsonString typ) ,("car",jsonList (map jsonInteger x)) ,("cdr",jsonList (map jsonInteger xs))] ListEndWHNF typ -> jsonObject [("constructor",jsonString "list-end"),("type",jsonString typ)] StringWHNF typ string -> jsonObject [("constructor",jsonString "string") ,("type",jsonString typ) ,("string",jsonString string)] TupleWHNF ty slots -> jsonObject [("constructor",jsonString "tuple") ,("type",jsonString ty) ,("slots" ,jsonList (map (\(typ,sid) -> jsonObject [("type",jsonString typ) ,("id",jsonList (map jsonInteger sid))]) slots))] ExceptionWHNF typ shown -> jsonObject [("constructor",jsonString "exception") ,("type",jsonString typ) ,("string",jsonString shown)] where jsonString :: String -> String jsonString = (\x -> "\"" ++ x ++ "\"") . go where go s1 = case s1 of (x:xs) | x < '\x20' -> '\\' : encControl x (go xs) ('"':xs) -> '\\' : '"' : go xs ('\\':xs) -> '\\' : '\\' : go xs (x:xs) -> x : go xs "" -> "" encControl x xs = case x of '\b' -> 'b' : xs '\f' -> 'f' : xs '\n' -> 'n' : xs '\r' -> 'r' : xs '\t' -> 't' : xs _ | x < '\x10' -> 'u' : '0' : '0' : '0' : hexxs | x < '\x100' -> 'u' : '0' : '0' : hexxs | x < '\x1000' -> 'u' : '0' : hexxs | otherwise -> 'u' : hexxs where hexxs = showHex (fromEnum x) xs jsonObject fields = "{" ++ intercalate ", " (map makeField fields) ++ "}" where makeField (name,value) = jsonString name ++ ": " ++ value jsonList xs = "[" ++ intercalate ", " xs ++ "]" jsonInteger :: Integer -> String jsonInteger = show