diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,340 @@ + GNU GENERAL PUBLIC LICENSE + Version 2, June 1991 + + Copyright (C) 1989, 1991 Free Software Foundation, Inc. + 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. By contrast, the GNU General Public +License is intended to guarantee your freedom to share and change free +software--to make sure the software is free for all its users. This +General Public License applies to most of the Free Software +Foundation's software and to any other program whose authors commit to +using it. (Some other Free Software Foundation software is covered by +the GNU Library General Public License instead.) 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It is safest +to attach them to the start of each source file to most effectively +convey the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + + Copyright (C) + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + + +Also add information on how to contact you by electronic and paper mail. + +If the program is interactive, make it output a short notice like this +when it starts in an interactive mode: + + Gnomovision version 69, Copyright (C) year name of author + Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, the commands you use may +be called something other than `show w' and `show c'; they could even be +mouse-clicks or menu items--whatever suits your program. + +You should also get your employer (if you work as a programmer) or your +school, if any, to sign a "copyright disclaimer" for the program, if +necessary. Here is a sample; alter the names: + + Yoyodyne, Inc., hereby disclaims all copyright interest in the program + `Gnomovision' (which makes passes at compilers) written by James Hacker. + + , 1 April 1989 + Ty Coon, President of Vice + +This General Public License does not permit incorporating your program into +proprietary programs. If your program is a subroutine library, you may +consider it more useful to permit linking proprietary applications with the +library. If this is what you want to do, use the GNU Library General +Public License instead of this License. diff --git a/Language/Haskell/Infix.hs b/Language/Haskell/Infix.hs new file mode 100644 --- /dev/null +++ b/Language/Haskell/Infix.hs @@ -0,0 +1,610 @@ +{------------------------------------------------------------------------------- + + Module: Language.Haskell.Infix + + Description: The Haskell Parser does not consider the fixity + of operators when parsing infix applications. + All infix applications are thus parsed as + if the operators were all left associative with + the same precedence. + + This module contains code for re-parsing infix + applications taking into account the fixity of + operators. + + The important algorithm is the well known + operator precedence parsing algorithm. See + comments in the code for more detailed + information. + + Primary Authors: Bernie Pope (bjpop@cs.mu.oz.au) + +-------------------------------------------------------------------------------} + + +module Language.Haskell.Infix ( infixer + , insertTopInfixDecls + , InfixMap + , plusInfixMap + , Fixity (..) + , showInfixMap + , infixMapToList + , emptyInfixMap + ) where + +import Language.Haskell.Syntax +import Data.FiniteMap + +-------------------------------------------------------------------------------- + +-- the fixity information +data Fixity = Fixity { fixity_assoc :: HsAssoc, + fixity_prec :: Int } + deriving Show + +-- a mapping from qualified operator names to fixity information +type InfixMap = FiniteMap HsQName Fixity + +plusInfixMap :: InfixMap -> InfixMap -> InfixMap +plusInfixMap = plusFM + +emptyInfixMap :: InfixMap +emptyInfixMap = emptyFM + +infixMapToList :: InfixMap -> [(HsQName, Fixity)] +infixMapToList = fmToList + +-- pretty crude illustration of infix map +showInfixMap :: InfixMap -> String +showInfixMap infixMap + = unlines $ map show mapList + where + mapList = infixMapToList infixMap + +-- fix up infix applications in a list of decls, to be called with +-- the topmost declarations in a module +infixer :: InfixMap -> [HsDecl] -> [HsDecl] +infixer infixMap decls + = runInfix infixMap $ mapM infixDecl decls + +-- this this the default fixity of an operator, to be used if the +-- operator does not have a corresponding fixity declaration +defaultFixity :: Fixity +defaultFixity = Fixity { fixity_assoc = HsAssocLeft, fixity_prec = 9 } + +-------------------------------------------------------------------------------- + +-- a monad for passing the infix map around + +data State = State { stateInfixMap :: InfixMap } + +newtype Infix a = Infix (State -> (a, State)) + +instance Monad Infix where + return a + = Infix (\state -> (a, state)) + Infix comp >>= fun + = Infix (\state -> + let (result, newState) = comp state + Infix comp' = fun result + in comp' newState) + +runInfix :: InfixMap -> Infix a -> a +runInfix infixMap (Infix comp) + = result + where + (result, _newState) = comp (State {stateInfixMap = infixMap}) + +select :: (State -> a) -> Infix a +select selector = Infix (\state -> (selector state, state)) + +updateState :: (State -> State) -> Infix () +updateState f = Infix (\state -> ((), f state)) + +getInfixMap :: Infix InfixMap +getInfixMap = select stateInfixMap + +getFixityQOp :: HsQOp -> Infix Fixity +getFixityQOp op + = getFixityQName $ qNameFromQOp op + +getFixityQName :: HsQName -> Infix Fixity +-- special consideration of (:) because it is not +-- explicitly given fixity info in the Prelude +-- this is the only one that needs special treatment +getFixityQName (Special HsCons) + = return $ Fixity {fixity_assoc = HsAssocRight, fixity_prec = 5} +getFixityQName name + = do infixMap <- getInfixMap + case lookupFM infixMap name of + Nothing -> return defaultFixity + Just fixity -> return fixity + +updateInfixMap :: [HsDecl] -> Infix () +updateInfixMap decls + = do oldInfixMap <- getInfixMap + let newInfixMap = insertLocalInfixDecls oldInfixMap decls + updateState (\state -> state {stateInfixMap = newInfixMap}) + +qNameFromQOp :: HsQOp -> HsQName +qNameFromQOp (HsQVarOp qName) = qName +qNameFromQOp (HsQConOp qName) = qName + +nameFromOp :: HsOp -> HsName +nameFromOp (HsVarOp name) = name +nameFromOp (HsConOp name) = name + +-------------------------------------------------------------------------------- + +-- crawl over expressions + +infixExp :: HsExp -> Infix HsExp +infixExp exp@(HsVar _) = return exp +infixExp exp@(HsCon _) = return exp +infixExp exp@(HsLit _) = return exp +infixExp exp@(HsInfixApp _ _ _) + = do infixList <- hsExpToInfixList exp + let eFix = opPrecParse HsInfixApp infixList + return eFix +infixExp (HsApp e1 e2) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + return $ HsApp e1Fix e2Fix +infixExp (HsNegApp e) + = do eFix <- infixExp e + return $ HsNegApp eFix +infixExp (HsLambda sloc pats e) + = do patsFix <- mapM infixPat pats + eFix <- infixExp e + return $ HsLambda sloc patsFix eFix +infixExp (HsLet decls e) + = do updateInfixMap decls + eFix <- infixExp e + _ <- mapM infixDecl decls + return $ HsLet decls eFix +infixExp (HsIf e1 e2 e3) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + e3Fix <- infixExp e3 + return $ HsIf e1Fix e2Fix e3Fix +infixExp (HsCase e alts) + = do eFix <- infixExp e + altsFix <- mapM infixAlt alts + return $ HsCase eFix altsFix +infixExp (HsDo stmts) + = do stmtsFix <- mapM infixStmt stmts + return $ HsDo stmtsFix +infixExp (HsTuple exps) + = do expsFix <- mapM infixExp exps + return $ HsTuple expsFix +infixExp (HsList exps) + = do expsFix <- mapM infixExp exps + return $ HsList expsFix +infixExp (HsParen exp) + = do expFix <- infixExp exp + return $ HsParen expFix +infixExp (HsLeftSection e qop) + = do eFix <- infixExp e + return $ HsLeftSection eFix qop +infixExp (HsRightSection qop e) + = do eFix <- infixExp e + return $ HsRightSection qop eFix +infixExp (HsRecConstr qName fieldUpdates) + = do fixFieldUpdates <- mapM infixFieldUpdate fieldUpdates + return $ HsRecConstr qName fixFieldUpdates +infixExp (HsRecUpdate e fieldUpdates) + = do eFix <- infixExp e + fixFieldUpdates <- mapM infixFieldUpdate fieldUpdates + return $ HsRecUpdate eFix fixFieldUpdates +infixExp (HsEnumFrom e) + = do eFix <- infixExp e + return $ HsEnumFrom eFix +infixExp (HsEnumFromTo e1 e2) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + return $ HsEnumFromTo e1Fix e2Fix +infixExp (HsEnumFromThen e1 e2) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + return $ HsEnumFromThen e1Fix e2Fix +infixExp (HsEnumFromThenTo e1 e2 e3) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + e3Fix <- infixExp e3 + return $ HsEnumFromThenTo e1Fix e2Fix e3Fix +infixExp (HsListComp e stmts) + = do eFix <- infixExp e + stmtsFix <- mapM infixStmt stmts + return $ HsListComp eFix stmtsFix +infixExp (HsExpTypeSig sloc e qualType) + = do eFix <- infixExp e + return $ HsExpTypeSig sloc eFix qualType +infixExp (HsAsPat name e) + = do eFix <- infixExp e + return $ HsAsPat name eFix +infixExp HsWildCard = return HsWildCard +infixExp (HsIrrPat e) + = do eFix <- infixExp e + return $ HsIrrPat eFix + + +-------------------------------------------------------------------------------- + +-- crawl over patterns + +infixPat :: HsPat -> Infix HsPat +infixPat pat@(HsPVar _) = return pat +infixPat pat@(HsPLit _) = return pat +infixPat (HsPNeg pat) + = do pFix <- infixPat pat + return $ HsPNeg pFix +infixPat pat@(HsPInfixApp _ _ _) + = do infixList <- hsPatToInfixList pat + let pFix = opPrecParse HsPInfixApp infixList + return pFix +infixPat (HsPApp qName pats) + = do patsFix <- mapM infixPat pats + return $ HsPApp qName patsFix +infixPat (HsPTuple pats) + = do patsFix <- mapM infixPat pats + return $ HsPTuple patsFix +infixPat (HsPList pats) + = do patsFix <- mapM infixPat pats + return $ HsPList patsFix +infixPat (HsPParen pat) + = do pFix <- infixPat pat + return $ HsPParen pFix +infixPat (HsPRec qName patFields) + = do fieldsFix <- mapM infixPatField patFields + return $ HsPRec qName fieldsFix +infixPat (HsPAsPat name pat) + = do pFix <- infixPat pat + return $ HsPAsPat name pFix +infixPat HsPWildCard = return HsPWildCard +infixPat (HsPIrrPat pat) + = do pFix <- infixPat pat + return $ HsPIrrPat pFix + +-- pattern fields +infixPatField :: HsPatField -> Infix HsPatField +infixPatField (HsPFieldPat qName pat) + = do pFix <- infixPat pat + return $ HsPFieldPat qName pFix + +-------------------------------------------------------------------------------- + +-- crawl over alternatives + +infixAlt :: HsAlt -> Infix HsAlt +infixAlt (HsAlt sloc pat guardedAlts decls) + = do pFix <- infixPat pat + fixAlts <- infixGuardedAlts guardedAlts + fixDecls <- mapM infixDecl decls + return $ HsAlt sloc pFix fixAlts fixDecls + +infixGuardedAlts :: HsGuardedAlts -> Infix HsGuardedAlts +infixGuardedAlts (HsUnGuardedAlt e) + = do eFix <- infixExp e + return $ HsUnGuardedAlt eFix +infixGuardedAlts (HsGuardedAlts gAlts) + = do fixGAlts <- mapM infixGuardedAlt gAlts + return $ HsGuardedAlts fixGAlts + +infixGuardedAlt :: HsGuardedAlt -> Infix HsGuardedAlt +infixGuardedAlt (HsGuardedAlt sloc e1 e2) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + return $ HsGuardedAlt sloc e1Fix e2Fix + +-------------------------------------------------------------------------------- + +-- crawl over statements + +infixStmt :: HsStmt -> Infix HsStmt +infixStmt (HsGenerator sloc pat e) + = do pFix <- infixPat pat + eFix <- infixExp e + return $ HsGenerator sloc pFix eFix +infixStmt (HsQualifier e) + = do eFix <- infixExp e + return $ HsQualifier eFix +infixStmt (HsLetStmt decls) + = do updateInfixMap decls + declsFix <- mapM infixDecl decls + return $ HsLetStmt declsFix + +-------------------------------------------------------------------------------- + +-- crawl over field updates + +infixFieldUpdate :: HsFieldUpdate -> Infix HsFieldUpdate +infixFieldUpdate (HsFieldUpdate qName e) + = do eFix <- infixExp e + return $ HsFieldUpdate qName eFix + +-------------------------------------------------------------------------------- + +-- crawl over declarations + +infixDecl :: HsDecl -> Infix HsDecl +infixDecl (HsFunBind matches) + = do fixMatches <- mapM infixMatch matches + return $ HsFunBind fixMatches +infixDecl (HsPatBind sloc pat rhs decls) + = do pFix <- infixPat pat + updateInfixMap decls + fixRhs <- infixRhs rhs + fixDecls <- mapM infixDecl decls + return $ HsPatBind sloc pFix fixRhs fixDecls +infixDecl (HsClassDecl sloc cntxt className args decls) + = do declsFix <- mapM infixDecl decls + return $ HsClassDecl sloc cntxt className args declsFix +infixDecl (HsInstDecl sloc cntxt className args decls) + = do declsFix <- mapM infixDecl decls + return $ HsInstDecl sloc cntxt className args declsFix +infixDecl otherDecl = return otherDecl + +-- matches +infixMatch :: HsMatch -> Infix HsMatch +infixMatch (HsMatch sloc name pats rhs decls) + = do patsFix <- mapM infixPat pats + updateInfixMap decls + fixRhs <- infixRhs rhs + fixDecls <- mapM infixDecl decls + return $ HsMatch sloc name patsFix fixRhs fixDecls + +-- rhs +infixRhs :: HsRhs -> Infix HsRhs +infixRhs (HsUnGuardedRhs e) + = do eFix <- infixExp e + return $ HsUnGuardedRhs eFix +infixRhs (HsGuardedRhss rhss) + = do rhssFix <- mapM infixGuardedRhs rhss + return $ HsGuardedRhss rhssFix + +-- guarded rhs +infixGuardedRhs :: HsGuardedRhs -> Infix HsGuardedRhs +infixGuardedRhs (HsGuardedRhs sloc e1 e2) + = do e1Fix <- infixExp e1 + e2Fix <- infixExp e2 + return $ HsGuardedRhs sloc e1Fix e2Fix + +-------------------------------------------------------------------------------- + +-- add new infix rules to an existing table +-- this is only for local infix decls (those not at the top-level of a +-- module). These decls only cause unqualified names to be entered +-- into the infix map. + +insertLocalInfixDecls :: InfixMap -> [HsDecl] -> InfixMap +insertLocalInfixDecls imap [] = imap +insertLocalInfixDecls imap (HsInfixDecl _ assoc prec ops : decls) + = insertLocalInfixDecls (insertLocalOps thisFixity ops imap) decls + where + thisFixity = Fixity { fixity_assoc = assoc, fixity_prec = prec } + insertLocalOps :: Fixity -> [HsOp] -> InfixMap -> InfixMap + insertLocalOps _fixity [] imap = imap + insertLocalOps fixity (op:ops) infixMap + = let opName = nameFromOp op + map1 = addToFM infixMap (UnQual opName) fixity + in insertLocalOps fixity ops map1 +insertLocalInfixDecls imap (_ : decls) + = insertLocalInfixDecls imap decls + +-- as above but for top-level infix decls (which (sadly) can also occur inside +-- class declarations)) +-- Top level infix decls cause unqualified AND +-- qualified names to be entered into the infix map +insertTopInfixDecls :: Module -> InfixMap -> [HsDecl] -> InfixMap +insertTopInfixDecls _ imap [] = imap +insertTopInfixDecls modName imap (HsInfixDecl _ assoc prec ops : decls) + = insertTopInfixDecls modName (insertTopOps modName thisFixity ops imap) decls + where + thisFixity :: Fixity + thisFixity = Fixity { fixity_assoc = assoc, fixity_prec = prec } + insertTopOps :: Module -> Fixity -> [HsOp] -> InfixMap -> InfixMap + insertTopOps _ _fixity [] imap = imap + insertTopOps modName fixity (op:ops) infixMap + = let opName = nameFromOp op + -- insert qualified and unqualified versions of the name + -- into the infix table + map1 = addToFM infixMap (UnQual opName) fixity + map2 = addToFM map1 (Qual modName $ opName) fixity + in insertTopOps modName fixity ops map2 +-- class decls can have infix decls and these are treated in the same way +-- as top-level infix decls +insertTopInfixDecls modName imap (HsClassDecl _sloc _cntxt _name _args classDecls : decls) + = insertTopInfixDecls modName (insertTopInfixDecls modName imap classDecls) decls +-- step over any other decl +insertTopInfixDecls modName imap (_ : decls) + = insertTopInfixDecls modName imap decls + +{------------------------------------------------------------------------------- + + Here is the important part. + + The parser does not take the fixity (precedence and associativity) of + infix operators into account when it parses a module. This is because + imported operators may have their own fixity, so to know all the fixity + information for a single module, the parser would have to know the fixity + information for imported modules - which would require partial parsing of + imported modules, and would be a mess. + + Instead it parses all infix applications as if they were left associative, + with each operator having the same precedence, for example: + + 1 + 2 ^ 4 * 6 - 8 + + would be parsed as: + + ((((1 + 2) ^ 4) * 6) - 8) + + This is clearly wrong. To fix this we re-parse the expression taking fixity + into account. + + The first step is to convert it into a more convenient form: from a parse tree + to a list of expressions (alternating between expression and operator): + + [Arg 1, + Op (+) HsAssocLeft 6, + Arg 2, + Op (^) HsAssocRight 8, + Arg 4, + Op (*) HsAssocLeft 7, + Arg 6, + Op (-) HsAssocLeft 6, + Arg 8] + + The conversion is done by hsExpToInfixList. This stage is not really necessary. + However, I feel that it does contribute to the clarity of the program, and + correctness is more important than efficiency here. + + The second step is to reparse this expression using the well known + operator precedence parsing technique. + + The basic idea is to introduce two stacks: one for expressions (the arguments + in between the operators), and one for operators. Parsing alternates between dealing with + the next expression and dealing with the next operator. + + Expressions are always pushed onto the stack when they are encountered as the next + item in the input list. + + Operators are pushed onto the operator stack iff they have a higher precedence than + the operator on top of the stack (or the stack is empty). + + If the next operator has a lower precedence than the top operator in the operator stack, + a reduction is performed. The top operator on the stack is applied to the two topmost + expressions on the expression stack, forming a new experssion (an infix application). + This new expression replaces the two top expressions on the expression stack, we then + continue. + + If the next operator and the top operator have the same precedence, then their + associativity determines what happens. If they are both left associative then a + reduction is performed. If they are both right associative then the next operator + is shifted. If they are a mixture of anything else (left, right, non-assoc) then + a syntax error has occurred. + + Two non-associative operators are allowed in sequence iff they have different precedences. + + eStack opStack input + {} {} 1 + 2 ^ 4 * 6 - 8 + 1 {} + 2 ^ 4 * 6 - 8 (shift exp) + 1 + 2 ^ 4 * 6 - 8 (shift op) + 1,2 + ^ 4 * 6 - 8 (shift exp) + 1,2 +,^ 4 * 6 - 8 (shift op) + 1,2,4 +,^ * 6 - 8 (shift exp) + 1,(2^4) + * 6 - 8 (reduce) + 1,(2^4) +,* 6 - 8 (shift op) + 1,(2^4),6 +,* - 8 (shift exp) + 1,((2^4)*6) + - 8 (reduce) + (1+((2^4)*6)) {} - 8 (reduce, b/c +,- are left associative) + (1+((2^4)*6)) - 8 (shift op) + (1+((2^4)*6)),8 - {} (shift exp) + ((1+((2^4)*6))-8) {} {} (reduce) + + The final state MUST have exactly one expression in the expression stack, + zero operators in the operator stack, and zero items left in the input. + + All other final states are horrible errors, though in our case some parsing + has already been done, and so some types of error will be caught earlier. + + Similar reasoning to the above applies for infix pattern applications, + as in: + + foo (x:y:z:zs) is parsed as foo ((((x:y):z):zs)), which is wrong. + The precedence parser has been made sufficiently generic to reparse + expressions and patterns. + +--------------------------------------------------------------------------------} + +{- here we just convert the syntax trees of patterns and expressions into + something more convenient to manipulate for the later stage of + precedence parsing -} + +-- an operator or an argument (for an operator) +-- generalised to support expressions and patterns +data InfixExp op arg + = Op op Fixity | Arg arg + deriving Show + +hsExpToInfixList :: HsExp -> Infix [InfixExp HsQOp HsExp] +hsExpToInfixList exp + = hsExpToInfixAcc exp [] + where + hsExpToInfixAcc :: HsExp -> [InfixExp HsQOp HsExp] -> Infix [InfixExp HsQOp HsExp] + hsExpToInfixAcc (HsInfixApp e1 op e2) acc + = do fixity <- getFixityQOp op + e2Fix <- infixExp e2 + hsExpToInfixAcc e1 (Op op fixity : Arg e2Fix : acc) + hsExpToInfixAcc exp acc + = do eFix <- infixExp exp + return $ Arg eFix : acc + +-- as above but for patterns +hsPatToInfixList :: HsPat -> Infix [InfixExp HsQName HsPat] +hsPatToInfixList pat + = hsPatToInfixAcc pat [] + where + hsPatToInfixAcc :: HsPat -> [InfixExp HsQName HsPat] -> Infix [InfixExp HsQName HsPat] + hsPatToInfixAcc (HsPInfixApp p1 op p2) acc + = do fixity <- getFixityQName op + p2Fix <- infixPat p2 + hsPatToInfixAcc p1 (Op op fixity : Arg p2Fix : acc) + hsPatToInfixAcc pat acc + = do pFix <- infixPat pat + return $ Arg pFix : acc + +-------------------------------------------------------------------------------- + +-- operator precedence parsing + +opPrecParse :: (arg -> op -> arg -> arg) -> [InfixExp op arg] -> arg +opPrecParse combiner exps + = reparseInfix combiner exps [] [] + where + reparseInfix :: (arg -> op -> arg -> arg) + -> [InfixExp op arg] + -> [(op, Fixity)] + -> [arg] + -> arg + -- successful termination + reparseInfix _combiner [] [] [arg] = arg + -- consume the remaining operators that have been stacked + reparseInfix combiner [] ((op,_fixity):opStack) (a1:a2:argStack) + = reparseInfix combiner [] opStack (combiner a2 op a1 : argStack) + -- always shift the expressions + reparseInfix combiner (Arg a : args) opStack argStack + = reparseInfix combiner args opStack (a : argStack) + -- empty operator stack, just shift the operator + reparseInfix combiner (Op thisOp thisFixity : rest) [] argStack + = reparseInfix combiner rest [(thisOp,thisFixity)] argStack + reparseInfix combiner (Op thisOp thisFixity : rest) (topOpStack:opStack) (topArg1:topArg2:argStack) + -- shift the operator + | thisPrec > topPrec + = reparseInfix combiner rest ((thisOp,thisFixity):topOpStack:opStack) + (topArg1:topArg2:argStack) + -- reduce + | thisPrec < topPrec + = reparseInfix combiner (Op thisOp thisFixity : rest) opStack + (combiner topArg2 topOp topArg1 : argStack) + -- equal precedence, check the associativity + | otherwise + = case (thisAssoc, topAssoc) of + -- reduce + (HsAssocLeft, HsAssocLeft) + -> reparseInfix combiner (Op thisOp thisFixity : rest) opStack + (combiner topArg2 topOp topArg1 : argStack) + -- shift + (HsAssocRight, HsAssocRight) + -> reparseInfix combiner rest ((thisOp,thisFixity):topOpStack:opStack) + (topArg1:topArg2:argStack) + -- this error needs fixing + _ -> error "Syntax error" + where + (topOp, topFixity) = topOpStack + topAssoc = fixity_assoc topFixity + topPrec = fixity_prec topFixity + thisAssoc = fixity_assoc thisFixity + thisPrec = fixity_prec thisFixity + -- XXX this error needs fixing + reparseInfix _ _ _ _ = error "Syntax error" diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,5 @@ +#!/usr/bin/runhaskell + +import Distribution.Simple + +main = defaultMainWithHooks defaultUserHooks diff --git a/infix.cabal b/infix.cabal new file mode 100644 --- /dev/null +++ b/infix.cabal @@ -0,0 +1,32 @@ +name: infix +version: 0.1 +synopsis: Infix expression re-parsing (for HsParser library) +description: The Haskell parser does not consider the fixity + of operators when parsing infix applications. + All infix applications are thus parsed as + if the operators were all left associative with + the same precedence. + + This module contains code for re-parsing infix + applications taking into account the fixity of + operators. + + The important algorithm is the well known + operator precedence parsing algorithm. See + comments in the code for more detailed + information. +category: Parsing +license: GPL +license-file: LICENSE +author: Bernie Pope +maintainer: None +homepage: http://www.cs.mu.oz.au/~bjpop/code.html + +build-depends: base, containers, haskell-src, FiniteMap +build-type: Simple +tested-with: GHC==6.5 + +exposed-modules: Language.Haskell.Infix + +ghc-options: -O2 -Wall -optl-Wl,-s +ghc-prof-options: -prof -auto-all