{-# LANGUAGE RankNTypes, GADTs, MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, FlexibleContexts, UndecidableInstances, NoMonomorphismRestriction, TypeSynonymInstances, ScopedTypeVariables #-} -- | This module contains basic instances for the class interface described in the "Text.ParserCombinators.UU.Core" module. -- It demonstates how to construct and maintain a state during parsing. In the state we store error messages, -- positional information and the actual input that is being parsed. -- Unless you have very specific wishes the module can be used as such. -- Since we make use of the "Data.ListLike" interface a wide variety of input structures can be handled. module Text.ParserCombinators.UU.BasicInstances( -- * Data Types Error (..), Str (..), Insertion (..), LineCol (..), LineColPos (..), -- * Types Parser, ParserTrafo, -- * Classes IsLocationUpdatedBy, -- * Functions createStr, show_expecting, pSatisfy, pRangeInsert, pRange, pSymInsert, pSym, pToken, pTokenCost, pMunch, ) where import Text.ParserCombinators.UU.Core import Data.Maybe import Data.Word import Debug.Trace import qualified Data.ListLike as LL -- * `Error` -- |The data type `Error` describes the various kinds of errors which can be generated by the instances in this module data Error pos = Inserted String pos Strings -- ^ @String@ was inserted at @pos@-ition, where we expected @Strings@ | Deleted String pos Strings -- ^ @String@ was deleted at @pos@-ition, where we expected @Strings@ | Replaced String String pos Strings -- ^ for future use | DeletedAtEnd String -- ^ the unconsumed part of the input was deleted instance (Show pos) => Show (Error pos) where show (Inserted s pos expecting) = "-- Inserted " ++ s ++ show_expecting pos expecting show (Deleted t pos expecting) = "-- Deleted " ++ t ++ show_expecting pos expecting show (Replaced old new pos expecting) = "-- Replaced " ++ old ++ " by "++ new ++ show_expecting pos expecting show (DeletedAtEnd t) = "-- The token " ++ t ++ " was not consumed by the parsing process." show_expecting :: Show pos => pos -> [String] -> String show_expecting pos [a] = " at position " ++ show pos ++ " expecting " ++ a show_expecting pos (a:as) = " at position " ++ show pos ++ " expecting one of [" ++ a ++ concat (map (", " ++) as) ++ "]" show_expecting pos [] = " expecting nothing" -- * The Stream data type -- | The data type `Str` holds the input data to be parsed, the current location, the error messages generated -- and whether it is ok to delete elements from the input. Since an insert/delete action is -- the same as a delete/insert action we try to avoid the first one. -- So: no deletes after an insert. data Str a s loc = Str { -- | the unconsumed part of the input input :: s, -- | the accumulated error messages msgs :: [Error loc], -- | the current input position pos :: loc, -- | we want to avoid deletions after insertions deleteOk :: !Bool } -- | A `Parser` is a parser that is prepared to accept "Data.Listlike" input; hence we can deal with @String@'s, @ByteString@'s, etc. type Parser a = (IsLocationUpdatedBy loc Char, LL.ListLike state Char) => P (Str Char state loc) a -- | A @`ParserTrafo` a b@ maps a @`Parser` a@ onto a @`Parser` b@. type ParserTrafo a b = (IsLocationUpdatedBy loc Char, LL.ListLike state Char) => P (Str Char state loc) a -> P (Str Char state loc) b -- | `createStr` initialises the input stream with the input data and the initial position. There are no error messages yet. createStr :: LL.ListLike s a => loc -> s -> Str a s loc createStr beginpos ls = Str ls [] beginpos True -- The first parameter is the current position, and the second parameter the part which has been removed from the input. instance IsLocationUpdatedBy Int Char where advance pos _ = pos + 1 instance IsLocationUpdatedBy Int Word8 where advance pos _ = pos + 1 data LineCol = LineCol !Int !Int deriving Show instance IsLocationUpdatedBy LineCol Char where advance (LineCol line pos) c = case c of '\n' -> LineCol (line+1) 0 '\t' -> LineCol line ( pos + 8 - (pos-1) `mod` 8) _ -> LineCol line (pos + 1) data LineColPos = LineColPos !Int !Int !Int deriving Show instance IsLocationUpdatedBy LineColPos Char where advance (LineColPos line pos abs) c = case c of '\n' -> LineColPos (line+1) 0 (abs + 1) '\t' -> LineColPos line (pos + 8 - (pos-1) `mod` 8) (abs + 1) _ -> LineColPos line (pos + 1) (abs + 1) instance IsLocationUpdatedBy loc a => IsLocationUpdatedBy loc [a] where advance = foldl advance instance (Show a, LL.ListLike s a) => Eof (Str a s loc) where eof (Str i _ _ _ ) = LL.null i deleteAtEnd (Str s msgs pos ok ) | LL.null s = Nothing | otherwise = Just (5, Str (LL.tail s) (msgs ++ [DeletedAtEnd (show (LL.head s))]) pos ok) instance StoresErrors (Str a s loc) (Error loc) where getErrors (Str inp msgs pos ok ) = (msgs, Str inp [] pos ok) instance HasPosition (Str a s loc) loc where getPos (Str inp msgs pos ok ) = pos -- | the @String@ describes what is being inserted, the @a@ parameter the value which is to be inserted and the @cost@ the prices to be paid. data Insertion a = Insertion String a Cost -- | `pSatisfy` describes and elementary parsing step. Its first parameter check whether the head element of the input can be recognised, -- and the second parameter how to proceed in case an element recognised by this parser is absent, -- and parsing may proceed by pretending such an element was present in the input anayway. pSatisfy :: forall loc state a .((Show a, loc `IsLocationUpdatedBy` a, LL.ListLike state a) => (a -> Bool) -> (Insertion a) -> P (Str a state loc) a) pSatisfy p (Insertion msg a cost) = pSymExt splitState (Succ (Zero Infinite)) Nothing where splitState :: forall r. ((a -> (Str a state loc) -> Steps r) -> (Str a state loc) -> Steps r) splitState k (Str tts msgs pos del_ok) = show_attempt ("Try Predicate: " ++ msg ++ " at position " ++ show pos ++ "\n") ( let ins exp = (cost, k a (Str tts (msgs ++ [Inserted (show a) pos exp]) pos False)) in if LL.null tts then Fail [msg] [ins] else let t = LL.head tts ts = LL.tail tts del exp = (4, splitState k (Str ts (msgs ++ [Deleted (show t) pos exp]) (advance pos t) True )) in if p t then show_symbol ("Accepting symbol: " ++ show t ++ " at position: " ++ show pos ++"\n") (Step 1 (k t (Str ts msgs (advance pos t) True))) else Fail [msg] (ins: if del_ok then [del] else []) ) -- | `pRangeInsert` recognises an element between a lower and an upper bound. Furthermore it can be specified what element -- is to be inserted in case such an element is not at the head of the input. pRangeInsert :: (Ord a, Show a, IsLocationUpdatedBy loc a, LL.ListLike state a) => (a, a) -> Insertion a -> P (Str a state loc) a pRangeInsert (low, high) = pSatisfy (\ t -> low <= t && t <= high) -- | `pRange` uses the information from the bounds to compute the `Insertion` information. pRange :: (Ord a, Show a, IsLocationUpdatedBy loc a, LL.ListLike state a) => (a, a) -> P (Str a state loc) a pRange lh@(low, high) = pRangeInsert lh (Insertion (show low ++ ".." ++ show high) low 5) -- | `pSymInsert` recognises a specific element. Furthermore it can be specified what element -- is to be inserted in case such an element is not at the head of the input. pSymInsert :: (Eq a,Show a, IsLocationUpdatedBy loc a, LL.ListLike state a) => a -> Insertion a -> P (Str a state loc) a pSymInsert t = pSatisfy (==t) -- | `pSym` recognises a specific element. Furthermore it can be specified what element. Information about `Insertion` is derived from the parameter. -- is to be inserted in case such an element is not at the head of the input. pSym :: (Eq a,Show a, IsLocationUpdatedBy loc a, LL.ListLike state a) => a -> P (Str a state loc) a pSym t = pSymInsert t (Insertion (show t) t 5) -- | `pMunchL` recognises the longest prefix of the input for which the passed predicate holds. The message parameter is used when tracing has been switched on. pMunchL :: forall loc state a .((Show a, loc `IsLocationUpdatedBy` a, LL.ListLike state a) => (a -> Bool) -> String -> P (Str a state loc) [a]) pMunchL p msg = pSymExt splitState (Zero Infinite) Nothing where splitState :: forall r. (([a] -> (Str a state loc) -> Steps r) -> (Str a state loc) -> Steps r) splitState k inp@(Str tts msgs pos del_ok) = show_attempt ("Try Munch: " ++ msg ++ "\n") ( let (fmunch, rest) = LL.span p tts munched = LL.toList fmunch l = length munched in if l > 0 then show_munch ("Accepting munch: " ++ msg ++ " " ++ show munched ++ show pos ++ "\n") (Step l (k munched (Str rest msgs (advance pos munched) (l>0 || del_ok)))) else show_munch ("Accepting munch: " ++ msg ++ " as emtty munch " ++ show pos ++ "\n") (k [] inp) ) -- | `pMunch` recognises the longest prefix of the input for which the passed predicate holds. The message parameer is used when tracing has been switched on. pMunch :: forall loc state a .((Show a, loc `IsLocationUpdatedBy` a, LL.ListLike state a) => (a -> Bool) -> P (Str a state loc) [a]) pMunch p = pMunchL p "" -- | `pTokenCost` succeeds if its parameter is a prefix of the input. pTokenCost :: forall loc state a .((Show a, Eq a, loc `IsLocationUpdatedBy` a, LL.ListLike state a) => [a] -> Int -> P (Str a state loc) [a]) pTokenCost as cost = if null as then error "Module: BasicInstances, function: pTokenCost; call with empty token" else pSymExt splitState (nat_length as) Nothing where tas :: state tas = LL.fromList as nat_length [] = Zero Infinite nat_length (_:as) = Succ (nat_length as) l = length as msg = show as splitState :: forall r. (([a] -> (Str a state loc) -> Steps r) -> (Str a state loc) -> Steps r) splitState k inp@(Str tts msgs pos del_ok) = show_attempt ("Try Token: " ++ show as ++ "\n") ( if LL.isPrefixOf tas tts then show_tokens ("Accepting token: " ++ show as ++"\n") (Step l (k as (Str (LL.drop l tts) msgs (advance pos as) True))) else let ins exp = (cost, k as (Str tts (msgs ++ [Inserted msg pos exp]) pos False)) in if LL.null tts then Fail [msg] [ins] else let t = LL.head tts ts = LL.tail tts del exp = (5, splitState k (Str ts (msgs ++ [Deleted (show t) pos exp]) (advance pos t) True)) in Fail [msg] (ins: if del_ok then [del] else []) ) pToken :: forall loc state a .((Show a, Eq a, loc `IsLocationUpdatedBy` a, LL.ListLike state a) => [a] -> P (Str a state loc) [a]) pToken as = pTokenCost as 5 {-# INLINE show_tokens #-} show_tokens :: String -> b -> b show_tokens m v = {- trace m -} v {-# INLINE show_munch #-} show_munch :: String -> b -> b show_munch m v = {- trace m -} v {-# INLINE show_symbol #-} show_symbol :: String -> b -> b show_symbol m v = {- trace m -} v {-# INLINE show_attempt #-} show_attempt m v = {- trace m -} v