> {-# LANGUAGE CPP #-}

-----------------------------------------------------------------------------
The Grammar data type.

(c) 1993-2001 Andy Gill, Simon Marlow
-----------------------------------------------------------------------------

Here is our mid-section datatype

> module Grammar (
> 	Name, isEmpty,
>
>	Production, Grammar(..), mangler,
>
>	LRAction(..), ActionTable, Goto(..), GotoTable, Priority(..),
>       Assoc(..),
>
>	errorName, errorTok, startName, firstStartTok, dummyTok,
>	eofName, epsilonTok
>	) where

> import GenUtils
> import AbsSyn
> import ParseMonad
> import AttrGrammar
> import AttrGrammarParser

> import Data.Array
> import Data.Char
> import Data.List
> import Prelude hiding (null, length, or, foldr, maximum, concat, concatMap, foldl, foldr1, foldl1, sum, all, elem)
> import Data.Maybe (fromMaybe)

#ifdef DEBUG

> import IOExts

#endif

> type Name = Int

> type Production = (Name,[Name],(String,[Int]),Priority)

> data Grammar
>       = Grammar {
>		productions 	  :: [Production],
>		lookupProdNo 	  :: Int -> Production,
>		lookupProdsOfName :: Name -> [Int],
>               token_specs 	  :: [(Name,String)],
>               terminals 	  :: [Name],
>               non_terminals 	  :: [Name],
>		starts		  :: [(String,Name,Name,Bool)],
>		types 		  :: Array Int (Maybe String),
>               token_names 	  :: Array Int String,
>		first_nonterm	  :: Name,
>		first_term 	  :: Name,
>               eof_term	  :: Name,
>               priorities        :: [(Name,Priority)],
>		token_type	  :: String,
>		imported_identity :: Bool,
>		monad		  :: (Bool,String,String,String,String),
>		expect		  :: Maybe Int,
>               attributes        :: [(String,String)],
>               attributetype     :: String,
>		lexer		  :: Maybe (String,String),
>		error_handler	  :: Maybe String
>	}

#ifdef DEBUG

> instance Show Grammar where
>       showsPrec _ (Grammar
>		{ productions		= p
>		, token_specs		= t
>               , terminals		= ts
>               , non_terminals		= nts
>		, starts		= starts
>		, types			= tys
>               , token_names		= e
>		, first_nonterm		= fnt
>		, first_term		= ft
>               , eof_term		= eof
>	 	})
>	 = showString "productions = "     . shows p
>        . showString "\ntoken_specs = "   . shows t
>        . showString "\nterminals = "     . shows ts
>        . showString "\nnonterminals = "  . shows nts
>        . showString "\nstarts = "        . shows starts
>        . showString "\ntypes = "         . shows tys
>        . showString "\ntoken_names = "   . shows e
>	 . showString "\nfirst_nonterm = " . shows fnt
>	 . showString "\nfirst_term = "    . shows ft
>        . showString "\neof = "           . shows eof
>	 . showString "\n"

#endif

> data Assoc = LeftAssoc | RightAssoc | None

#ifdef DEBUG

>	deriving Show

#endif

> data Priority = No | Prio Assoc Int

#ifdef DEBUG

>	deriving Show

#endif

> instance Eq Priority where
>   No == No = True
>   Prio _ i == Prio _ j = i == j
>   _ == _ = False

> mkPrio :: Int -> Directive a -> Priority
> mkPrio i (TokenNonassoc _) = Prio None i
> mkPrio i (TokenRight _) = Prio RightAssoc i
> mkPrio i (TokenLeft _) = Prio LeftAssoc i
> mkPrio i _ = error "Panic: impossible case in mkPrio"

-----------------------------------------------------------------------------
-- Magic name values

All the tokens in the grammar are mapped onto integers, for speed.
The namespace is broken up as follows:

epsilon		= 0
error		= 1
dummy		= 2
%start 		= 3..s
non-terminals 	= s..n
terminals 	= n..m
%eof 		= m

These numbers are deeply magical, change at your own risk.  Several
other places rely on these being arranged as they are, including
ProduceCode.lhs and the various HappyTemplates.

Unfortunately this means you can't tell whether a given token is a
terminal or non-terminal without knowing the boundaries of the
namespace, which are kept in the Grammar structure.

In hindsight, this was probably a bad idea.

> startName = "%start" -- with a suffix, like %start_1, %start_2 etc.
> eofName   = "%eof"
> errorName = "error"
> dummyName = "%dummy"  -- shouldn't occur in the grammar anywhere

> firstStartTok, dummyTok, errorTok, epsilonTok :: Name
> firstStartTok   = 3
> dummyTok        = 2
> errorTok    	  = 1
> epsilonTok 	  = 0

> isEmpty :: Name -> Bool
> isEmpty n | n == epsilonTok = True
>	    | otherwise       = False

-----------------------------------------------------------------------------
-- The Mangler

This bit is a real mess, mainly because of the error message support.

> m `thenE` k
> 	= case m of
>		Failed e    -> Failed e
>		Succeeded a -> case k a of
>				Failed e -> Failed e
>				Succeeded b -> Succeeded b

> m `parE` k
> 	= case m of
>		Failed e    -> case k (error "parE") of
>				Failed e' -> Failed (e ++ e')
>				Succeeded _ -> Failed e
>		Succeeded a -> case k a of
>				Failed e -> Failed e
>				Succeeded b -> Succeeded b

> parEs [] = Succeeded []
> parEs (x:xs) = x `parE` \x' ->
>		 parEs xs `parE` \xs' ->
>		 Succeeded (x':xs')

> failMap :: (b -> c) -> MaybeErr a [b] -> MaybeErr a [c]
> failMap f e = case e of
>   		  Succeeded a -> Succeeded a
>		  Failed s -> Failed (map f s)


> mangler :: FilePath -> AbsSyn -> MaybeErr Grammar [String]
> mangler file (AbsSyn hd dirs rules tl) =

>	  -- add filename to all error messages
>	failMap (\s -> file ++ ": " ++ s) $

>	checkRules ([n | (n,_,_) <- rules]) "" [] `thenE` \nonterm_strs  ->

>	let

>       terminal_strs  = concat (map getTerm dirs) ++ [eofName]

>	n_starts   = length starts
>	n_nts      = length nonterm_strs
>	n_ts       = length terminal_strs
>	first_nt   = firstStartTok + n_starts
>	first_t    = first_nt + n_nts
>	last_start = first_nt - 1
>	last_nt    = first_t  - 1
>	last_t     = first_t + n_ts - 1

>	start_names    = [ firstStartTok .. last_start ]
>       nonterm_names  = [ first_nt .. last_nt ]
>       terminal_names = [ first_t .. last_t ]

>	starts	    = case getParserNames dirs of
>			[] -> [TokenName "happyParse" Nothing False]
>			ns -> ns
>
>	start_strs  = [ startName++'_':p  | (TokenName p _ _) <- starts ]

Build up a mapping from name values to strings.

>       name_env = (errorTok, errorName) :
>		   (dummyTok, dummyName) :
>		   zip start_names    start_strs ++
>		   zip nonterm_names  nonterm_strs ++
>		   zip terminal_names terminal_strs

>	lookupName :: String -> [Name]
>	lookupName n = [ t | (t,r) <- name_env, r == n ]

>       mapToName str =
>             case lookupName str  of
>                [a] -> Succeeded a
>                []  -> Failed ["unknown identifier `" ++ str ++ "'"]
>                _   -> Failed ["multiple use of `" ++ str ++ "'"]

Start symbols...

>		-- default start token is the first non-terminal in the grammar
>	lookupStart (TokenName s Nothing  _) = Succeeded first_nt
>	lookupStart (TokenName s (Just n) _) = mapToName n
>	in

>	parEs (map lookupStart starts)	`thenE` \ start_toks ->

>	let
>	parser_names   = [ s | TokenName s _ _ <- starts ]
>	start_partials = [ b | TokenName _ _ b <- starts ]
>	start_prods = zipWith (\nm tok -> (nm, [tok], ("no code",[]), No))
>			 start_names start_toks

Deal with priorities...

>       priodir = zip [1..] (getPrios dirs)
>
>       prios = [ (name,mkPrio i dir)
>               | (i,dir) <- priodir
>               , nm <- AbsSyn.getPrioNames dir
>		, name <- lookupName nm
>		]

>       prioByString = [ (name, mkPrio i dir)
>                      | (i,dir) <- priodir
>                      , name <- AbsSyn.getPrioNames dir
>                      ]

Translate the rules from string to name-based.

>	convNT (nt, prods, ty)
>	  = mapToName nt `thenE` \nt' ->
>	    Succeeded (nt', prods, ty)
>
>       attrs = getAttributes dirs
>       attrType = fromMaybe "HappyAttrs" (getAttributetype dirs)
>
> 	transRule (nt, prods, ty)
>   	  = parEs (map (finishRule nt) prods)
>
>	finishRule nt (lhs,code,line,prec)
>	  = failMap (addLine line) $
>          parEs (map mapToName lhs)   `parE`  \lhs' ->
>          checkCode (length lhs) lhs' nonterm_names code attrs `thenE`  \code' ->
>	    case mkPrec lhs' prec of
>		Left s  -> Failed ["Undeclared precedence token: " ++ s]
>		Right p -> Succeeded (nt, lhs', code', p)
>
>       mkPrec :: [Name] -> Maybe String -> Either String Priority
>       mkPrec lhs prio =
>             case prio of
>               Nothing -> case filter (flip elem terminal_names) lhs of
>                            [] -> Right No
>                            xs -> case lookup (last xs) prios of
>                                    Nothing -> Right No
>                                    Just p  -> Right p
>               Just s -> case lookup s prioByString of
>                           Nothing -> Left s
>                           Just p -> Right p
>	in

>       parEs (map convNT rules)    `thenE` \rules1 ->
>	parEs (map transRule rules1) `thenE` \rules2 ->

>	let
>	tys = accumArray (\a b -> b) Nothing (first_nt, last_nt)
>			[ (nm, Just ty) | (nm, _, Just ty) <- rules1 ]

>	env_array :: Array Int String
>	env_array = array (errorTok, last_t) name_env
>	in

Get the token specs in terms of Names.

>	let
>	fixTokenSpec (a,b) = mapToName a `thenE` \a -> Succeeded (a,b)
>	in
>       parEs (map fixTokenSpec (getTokenSpec dirs)) `thenE` \tokspec ->

>	let
>	   ass = combinePairs [ (a,no)
>			      | ((a,_,_,_),no) <- zip productions [0..] ]
>	   arr = array (firstStartTok, length ass - 1 + firstStartTok) ass

>	   lookup_prods :: Name -> [Int]
>	   lookup_prods x | x >= firstStartTok && x < first_t = arr ! x
>	   lookup_prods _ = error "lookup_prods"
>
>	   productions = start_prods ++ concat rules2
>	   prod_array  = listArray' (0,length productions-1) productions
>	in

>	Succeeded (Grammar {
>		productions 	  = productions,
>		lookupProdNo   	  = (prod_array !),
>		lookupProdsOfName = lookup_prods,
>               token_specs	  = tokspec,
>               terminals	  = errorTok : terminal_names,
>               non_terminals	  = start_names ++ nonterm_names,
>				  	-- INCLUDES the %start tokens
>		starts		  = zip4 parser_names start_names start_toks
>					start_partials,
>		types		  = tys,
>               token_names	  = env_array,
>		first_nonterm	  = first_nt,
>		first_term	  = first_t,
>               eof_term	  = last terminal_names,
>               priorities        = prios,
>		imported_identity		  = getImportedIdentity dirs,
>		monad		  = getMonad dirs,
>		lexer		  = getLexer dirs,
>		error_handler	  = getError dirs,
>		token_type	  = getTokenType dirs,
>               expect            = getExpect dirs,
>               attributes        = attrs,
>               attributetype     = attrType
>	})

For combining actions with possible error messages.

> addLine :: Int -> String -> String
> addLine l s = show l ++ ": " ++ s

> getTerm (TokenSpec stuff) = map fst stuff
> getTerm _                 = []

So is this.

> checkRules (name:rest) above nonterms
>       | name == above = checkRules rest name nonterms
>       | name `elem` nonterms
>		= Failed ["Multiple rules for `" ++ name ++ "'"]
>       | otherwise = checkRules rest name (name : nonterms)

> checkRules [] _ nonterms = Succeeded (reverse nonterms)


-----------------------------------------------------------------------------
-- If any attribute directives were used, we are in an attribute grammar, so
-- go do special processing.  If not, pass on to the regular processing routine

> checkCode :: Int -> [Name] -> [Name] -> String -> [(String,String)] -> MaybeErr (String,[Int]) [String]
> checkCode arity lhs nonterm_names code []    = doCheckCode arity code
> checkCode arity lhs nonterm_names code attrs = rewriteAttributeGrammar arity lhs nonterm_names code attrs

------------------------------------------------------------------------------
-- Special processing for attribute grammars.  We re-parse the body of the code
-- block and output the nasty-looking record manipulation and let binding goop
--

> rewriteAttributeGrammar :: Int -> [Name] -> [Name] -> String -> [(String,String)] -> MaybeErr (String,[Int]) [String]
> rewriteAttributeGrammar arity lhs nonterm_names code attrs =

   first we need to parse the body of the code block

>     case runP agParser code 0 of
>        FailP msg  -> Failed [ "error in attribute grammar rules: "++msg ]
>        OkP rules  ->

   now we break the rules into three lists, one for synthesized attributes,
   one for inherited attributes, and one for conditionals

>            let (selfRules,subRules,conditions) = partitionRules [] [] [] rules
>                attrNames = map fst attrs
>                defaultAttr = head attrNames

   now check that $i references are in range

>            in parEs (map checkArity (mentionedProductions rules)) `thenE` \prods ->

   and output the rules

>                formatRules arity attrNames defaultAttr
>                            allSubProductions selfRules
>                            subRules conditions `thenE` \rulesStr ->

   return the munged code body and all sub-productions mentioned

>               Succeeded (rulesStr,nub (allSubProductions++prods))


>    where partitionRules a b c [] = (a,b,c)
>          partitionRules a b c (RightmostAssign attr toks : xs) = partitionRules a (SubAssign (arity,attr) toks : b) c xs
>          partitionRules a b c (x@(SelfAssign _ _ )  : xs) = partitionRules (x:a) b c xs
>          partitionRules a b c (x@(SubAssign _ _)    : xs) = partitionRules a (x:b) c xs
>          partitionRules a b c (x@(Conditional _)    : xs) = partitionRules a b (x:c) xs

>          allSubProductions             = map (+1) (findIndices (`elem` nonterm_names) lhs)

>          mentionedProductions rules    = [ i | (AgTok_SubRef (i,_)) <- concat (map getTokens rules) ]

>          getTokens (SelfAssign _ toks)      = toks
>          getTokens (SubAssign _ toks)       = toks
>          getTokens (Conditional toks)       = toks
>          getTokens (RightmostAssign _ toks) = toks
>
>          checkArity x = if x <= arity then Succeeded x else Failed [show x++" out of range"]



------------------------------------------------------------------------------------
-- Actually emit the code for the record bindings and conditionals
--

> formatRules :: Int -> [String] -> String -> [Name]
>             -> [AgRule] -> [AgRule] -> [AgRule]
>             -> MaybeErr String [String]

> formatRules arity attrNames defaultAttr prods selfRules subRules conditions = Succeeded $
>     concat [ "\\happyInhAttrs -> let { "
>            , "happySelfAttrs = happyInhAttrs",formattedSelfRules
>            , subProductionRules
>            , "; happyConditions = ", formattedConditions
>            , " } in (happyConditions,happySelfAttrs)"
>            ]
>
>  where formattedSelfRules = case selfRules of [] -> []; _ -> "{ "++formattedSelfRules'++" }"
>        formattedSelfRules' = concat $ intersperse ", " $ map formatSelfRule selfRules
>        formatSelfRule (SelfAssign [] toks)   = defaultAttr++" = "++(formatTokens toks)
>        formatSelfRule (SelfAssign attr toks) = attr++" = "++(formatTokens toks)

>        subRulesMap :: [(Int,[(String,[AgToken])])]
>        subRulesMap = map     (\l   -> foldr (\ (_,x) (i,xs) -> (i,x:xs))
>                                             (fst $ head l,[snd $ head l])
>                                             (tail l) ) .
>                      groupBy (\x y -> (fst x) == (fst y)) .
>                      sortBy  (\x y -> compare (fst x) (fst y)) .
>                      map     (\(SubAssign (i,id) toks) -> (i,(id,toks))) $ subRules

>        subProductionRules = concat $ map formatSubRules prods

>        formatSubRules i =
>           let attrs = fromMaybe [] . lookup i $ subRulesMap
>               attrUpdates' = concat $ intersperse ", " $ map (formatSubRule i) attrs
>               attrUpdates  = case attrUpdates' of [] -> []; x -> "{ "++x++" }"
>           in concat ["; (happyConditions_",show i,",happySubAttrs_",show i,") = ",mkHappyVar i
>                     ," happyEmptyAttrs"
>                     , attrUpdates
>                     ]
>
>        formattedConditions = concat $ intersperse "++" $ localConditions : (map (\i -> "happyConditions_"++(show i)) prods)
>        localConditions = "["++(concat $ intersperse ", " $ map formatCondition conditions)++"]"
>        formatCondition (Conditional toks) = formatTokens toks

>        formatSubRule i ([],toks)   = defaultAttr++" = "++(formatTokens toks)
>        formatSubRule i (attr,toks) = attr++" = "++(formatTokens toks)

>        formatTokens tokens = concat (map formatToken tokens)

>        formatToken AgTok_LBrace           =  "{ "
>        formatToken AgTok_RBrace           = "} "
>        formatToken AgTok_Where            = "where "
>        formatToken AgTok_Semicolon        = "; "
>        formatToken AgTok_Eq               = "="
>        formatToken (AgTok_SelfRef [])     = "("++defaultAttr++" happySelfAttrs) "
>        formatToken (AgTok_SelfRef x)      = "("++x++" happySelfAttrs) "
>        formatToken (AgTok_RightmostRef x) = formatToken (AgTok_SubRef (arity,x))
>        formatToken (AgTok_SubRef (i,[]))
>            | i `elem` prods = "("++defaultAttr++" happySubAttrs_"++(show i)++") "
>            | otherwise      = mkHappyVar i ++ " "
>        formatToken (AgTok_SubRef (i,x))
>            | i `elem` prods = "("++x++" happySubAttrs_"++(show i)++") "
>            | otherwise      = error "lhs "++(show i)++" is not a non-terminal"
>        formatToken (AgTok_Unknown x)     = x++" "


-----------------------------------------------------------------------------
-- Check for every $i that i is <= the arity of the rule.

-- At the same time, we collect a list of the variables actually used in this
-- code, which is used by the backend.

> doCheckCode :: Int -> String -> MaybeErr (String, [Int]) [String]
> doCheckCode arity code = go code "" []
>   where go code acc used =
>           case code of
>		[] -> Succeeded (reverse acc, used)
>
>		'"'  :r    -> case reads code :: [(String,String)] of
>				 []      -> go r ('"':acc) used
>				 (s,r):_ -> go r (reverse (show s) ++ acc) used
>		a:'\'' :r | isAlphaNum a -> go r ('\'':a:acc) used
>		'\'' :r    -> case reads code :: [(Char,String)] of
>				 []      -> go r ('\'':acc) used
>				 (c,r):_ -> go r (reverse (show c) ++ acc) used
>		'\\':'$':r -> go r ('$':acc) used
>
>		'$':'>':r -- the "rightmost token"
>			| arity == 0 -> Failed [ "$> in empty rule" ]
>			| otherwise  -> go r (reverse (mkHappyVar arity) ++ acc)
>					 (arity : used)
>
>		'$':r@(i:_) | isDigit i ->
>			case reads r :: [(Int,String)] of
>			  (j,r):_ ->
>			     if j > arity
>			   	  then Failed [ '$': show j ++ " out of range" ]
>				 	`parE` \_ -> go r acc used
>			   	  else go r (reverse (mkHappyVar j) ++ acc)
>					 (j : used)
>
>		c:r  -> go r (c:acc) used

> mkHappyVar n 	= "happy_var_" ++ show n

-----------------------------------------------------------------------------
-- Internal Reduction Datatypes

> data LRAction = LR'Shift Int Priority -- state number and priority
>               | LR'Reduce Int Priority-- rule no and priority
>               | LR'Accept             -- :-)
>               | LR'Fail               -- :-(
>               | LR'MustFail           -- :-(
>		| LR'Multiple [LRAction] LRAction	-- conflict
>       deriving(Eq

#ifdef DEBUG

>	,Show

#endif

>	)

> type ActionTable = Array Int{-state-} (Array Int{-terminal#-} LRAction)

 instance Text LRAction where
   showsPrec _ (LR'Shift i _)  = showString ("s" ++ show i)
   showsPrec _ (LR'Reduce i _)
       = showString ("r" ++ show i)
   showsPrec _ (LR'Accept)     = showString ("acc")
   showsPrec _ (LR'Fail)       = showString (" ")
 instance Eq LRAction where { (==) = primGenericEq }

> data Goto = Goto Int | NoGoto
>       deriving(Eq

#ifdef DEBUG

>	,Show

#endif

>	)

> type GotoTable = Array Int{-state-} (Array Int{-nonterminal #-} Goto)
