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-----------------------------------------------------------------------------
-- $Id: HsParseUtils.lhs,v 1.2 2002/04/10 16:10:26 simonmar Exp $
--
-- (c) The GHC Team 1997-2000
--
-- Utilities for the Haskell parser.
--
-----------------------------------------------------------------------------
ToDo: Polish readInteger, readRational
\begin{code}
module HsParseUtils (
parseError -- String -> Pa
, splitTyConApp -- HsType -> P (HsName,[HsType])
, mkRecConstrOrUpdate -- HsExp -> [HsFieldUpdate] -> P HsExp
, checkPrec -- String -> P String
, checkContext -- HsType -> P HsContext
, checkAssertion -- HsType -> P HsAsst
, checkDataHeader -- HsType -> P (HsContext,HsName,[HsName])
, checkSimple -- HsType -> [HsName] -> P ((HsName,[HsName]))
, checkPattern -- HsExp -> P HsPat
, checkPatterns -- [HsExp] -> P [HsPat]
, checkExpr -- HsExp -> P HsExp
, checkValDef -- (SrcLoc, HsExp, HsRhs, [HsDecl]) -> P HsDecl
, checkUnQual -- HsQName -> P HsName
, readInteger -- String -> Integer
, readRational -- String -> Rational
, toVarHsName -- HsName -> HsName
, toTyClsHsName -- HsName -> HsName
) where
import HsSyn
import HsParseMonad
import Char(isDigit,isOctDigit,isHexDigit,digitToInt)
import Ratio
\end{code}
\begin{code}
parseError :: String -> P a
parseError s = \r (SrcLoc y x) ->
failP (show y ++ ":" ++ show x ++ ": " ++ s) r (SrcLoc y x)
splitTyConApp :: HsType -> P (HsName,[HsType])
splitTyConApp t = split t []
where
split :: HsType -> [HsType] -> P (HsName,[HsType])
split (HsTyApp t u) ts = split t (u:ts)
split (HsTyCon (UnQual t)) ts = returnP (t,ts)
-- to cope with data [] = [] | a:[a]
split (HsTyCon (Qual m t)) ts = returnP (t,ts)
split _ _ = parseError "Illegal data/newtype declaration"
-----------------------------------------------------------------------------
-- Various Syntactic Checks
checkContext :: HsType -> P HsContext
checkContext (HsTyTuple True ts) =
mapP checkAssertion ts `thenP` \cs ->
returnP cs
checkContext t =
checkAssertion t `thenP` \c ->
returnP [c]
-- Changed for multi-parameter type classes
checkAssertion :: HsType -> P HsAsst
checkAssertion = checkAssertion' []
where checkAssertion' ts (HsTyCon c) = returnP (c,ts)
checkAssertion' ts (HsTyApp a t) = checkAssertion' (t:ts) a
checkAssertion' _ _ = parseError "Illegal class assertion"
checkDataHeader :: HsType -> P (HsContext,HsName,[HsName])
checkDataHeader (HsForAllType Nothing cs t) =
checkSimple t [] `thenP` \(c,ts) ->
returnP (cs,c,ts)
checkDataHeader t =
checkSimple t [] `thenP` \(c,ts) ->
returnP ([],c,ts)
checkSimple :: HsType -> [HsName] -> P ((HsName,[HsName]))
checkSimple (HsTyApp l (HsTyVar a)) xs = checkSimple l (a:xs)
checkSimple (HsTyCon (UnQual t)) xs = returnP (t,xs)
checkSimple (HsTyCon (Qual m t)) xs = returnP (t,xs)
checkSimple _ _ = parseError "Illegal data/newtype declaration"
-----------------------------------------------------------------------------
-- Checking Patterns.
-- We parse patterns as expressions and check for valid patterns below,
-- converting the expression into a pattern at the same time.
checkPattern :: HsExp -> P HsPat
checkPattern e = checkPat e []
checkPatterns :: [HsExp] -> P [HsPat]
checkPatterns es = mapP checkPattern es
checkPat :: HsExp -> [HsPat] -> P HsPat
checkPat (HsCon c) args = returnP (HsPApp c args)
checkPat (HsApp f x) args = checkPat x [] `thenP` \x -> checkPat f (x:args)
checkPat e [] = case e of
HsVar (UnQual x) -> returnP (HsPVar x)
HsLit l -> returnP (HsPLit l)
HsInfixApp l op r -> checkPat l [] `thenP` \l ->
checkPat r [] `thenP` \r ->
case op of
HsCon c -> returnP (HsPInfixApp l c r)
_ -> patFail
HsTuple b es -> mapP (\e -> checkPat e []) es `thenP` \ps ->
returnP (HsPTuple b ps)
HsList es -> mapP (\e -> checkPat e []) es `thenP` \ps ->
returnP (HsPList ps)
HsParen e -> checkPat e [] `thenP` (returnP . HsPParen)
HsAsPat n e -> checkPat e [] `thenP` (returnP . HsPAsPat n)
HsWildCard -> returnP HsPWildCard
HsIrrPat e -> checkPat e [] `thenP` (returnP . HsPIrrPat)
HsRecConstr c fs -> mapP checkPatField fs `thenP` \fs ->
returnP (HsPRec c fs)
HsNegApp (HsLit l) -> returnP (HsPNeg (HsPLit l))
HsExpTypeSig l e ty -> checkPat e [] `thenP` \e ->
returnP (HsPTypeSig e ty)
_ -> patFail
checkPat _ _ = patFail
checkPatField :: HsFieldUpdate -> P HsPatField
checkPatField (HsFieldUpdate n e) =
checkPat e [] `thenP` \p ->returnP (HsPFieldPat n p)
patFail = parseError "Parse error in pattern"
-----------------------------------------------------------------------------
-- Check Expression Syntax
checkExpr :: HsExp -> P HsExp
checkExpr e = case e of
HsVar _ -> returnP e
HsCon _ -> returnP e
HsLit _ -> returnP e
HsInfixApp e1 e2 e3 -> check3Exprs e1 e2 e3 HsInfixApp
HsApp e1 e2 -> check2Exprs e1 e2 HsApp
HsNegApp e -> check1Expr e HsNegApp
HsLambda ps e -> check1Expr e (HsLambda ps)
HsLet bs e -> check1Expr e (HsLet bs)
HsIf e1 e2 e3 -> check3Exprs e1 e2 e3 HsIf
HsCase e alts -> mapP checkAlt alts `thenP` \alts ->
checkExpr e `thenP` \e ->
returnP (HsCase e alts)
HsDo stmts -> mapP checkStmt stmts `thenP` (returnP . HsDo)
HsTuple b es -> checkManyExprs es (HsTuple b)
HsList es -> checkManyExprs es HsList
HsParen e -> check1Expr e HsParen
HsLeftSection e1 e2 -> check2Exprs e1 e2 HsLeftSection
HsRightSection e1 e2 -> check2Exprs e1 e2 HsRightSection
HsRecConstr c fields -> mapP checkField fields `thenP` \fields ->
returnP (HsRecConstr c fields)
HsRecUpdate e fields -> mapP checkField fields `thenP` \fields ->
checkExpr e `thenP` \e ->
returnP (HsRecUpdate e fields)
HsEnumFrom e -> check1Expr e HsEnumFrom
HsEnumFromTo e1 e2 -> check2Exprs e1 e2 HsEnumFromTo
HsEnumFromThen e1 e2 -> check2Exprs e1 e2 HsEnumFromThen
HsEnumFromThenTo e1 e2 e3 -> check3Exprs e1 e2 e3 HsEnumFromThenTo
HsListComp e stmts -> mapP checkStmt stmts `thenP` \stmts ->
checkExpr e `thenP` \e ->
returnP (HsListComp e stmts)
HsExpTypeSig loc e ty -> checkExpr e `thenP` \e ->
returnP (HsExpTypeSig loc e ty)
_ -> parseError "parse error in expression"
-- type signature for polymorphic recursion!!
check1Expr :: HsExp -> (HsExp -> a) -> P a
check1Expr e f = checkExpr e `thenP` (returnP . f)
check2Exprs :: HsExp -> HsExp -> (HsExp -> HsExp -> a) -> P a
check2Exprs e1 e2 f =
checkExpr e1 `thenP` \e1 ->
checkExpr e2 `thenP` \e2 ->
returnP (f e1 e2)
check3Exprs :: HsExp -> HsExp -> HsExp -> (HsExp -> HsExp -> HsExp -> a) -> P a
check3Exprs e1 e2 e3 f =
checkExpr e1 `thenP` \e1 ->
checkExpr e2 `thenP` \e2 ->
checkExpr e3 `thenP` \e3 ->
returnP (f e1 e2 e3)
checkManyExprs es f =
mapP checkExpr es `thenP` \es ->
returnP (f es)
checkAlt (HsAlt loc p galts bs)
= checkGAlts galts `thenP` \galts -> returnP (HsAlt loc p galts bs)
checkGAlts (HsUnGuardedAlt e) = check1Expr e HsUnGuardedAlt
checkGAlts (HsGuardedAlts galts)
= mapP checkGAlt galts `thenP` (returnP . HsGuardedAlts)
checkGAlt (HsGuardedAlt loc stmts e) =
mapP checkStmt stmts `thenP` \stmts ->
checkExpr e `thenP` \e ->
returnP (HsGuardedAlt loc stmts e)
checkStmt (HsGenerator p e) = check1Expr e (HsGenerator p)
checkStmt (HsQualifier e) = check1Expr e HsQualifier
checkStmt s@(HsLetStmt bs) = returnP s
checkField (HsFieldUpdate n e) = check1Expr e (HsFieldUpdate n)
-----------------------------------------------------------------------------
-- Check Equation Syntax
checkValDef :: (SrcLoc, HsExp, HsRhs, [HsDecl]) -> P HsDecl
checkValDef (srcloc, lhs, rhs, whereBinds) =
case isFunLhs lhs [] of
Just (f,es) -> checkPatterns es `thenP` \ps ->
returnP (HsFunBind [HsMatch srcloc f ps rhs whereBinds])
Nothing -> checkPattern lhs `thenP` \lhs ->
returnP (HsPatBind srcloc lhs rhs whereBinds)
-- A variable binding is parsed as an HsPatBind.
isFunLhs (HsInfixApp l (HsVar op) r) es = Just (op, l:r:es)
isFunLhs (HsApp (HsVar f) e) es = Just (f,e:es)
isFunLhs (HsApp (HsParen f) e) es = isFunLhs f (e:es)
isFunLhs (HsApp f e) es = isFunLhs f (e:es)
isFunLhs _ _ = Nothing
-----------------------------------------------------------------------------
-- Check that an identifier or symbol is unqualified.
-- For occasions when doing this in the grammar would cause conflicts.
checkUnQual :: HsQName -> P HsName
checkUnQual (Qual _ _) = parseError "Illegal qualified name"
checkUnQual (UnQual n) = returnP n
-----------------------------------------------------------------------------
-- Miscellaneous utilities
toVarHsName :: HsName -> HsName
toVarHsName (HsTyClsName n) = HsVarName n
toVarHsName n = n
toTyClsHsName :: HsName -> HsName
toTyClsHsName (HsVarName n) = HsTyClsName n
toTyClsHsName n = n
checkPrec :: Integer -> P ()
checkPrec i | i >= 0 && i <= 9 = returnP ()
checkPrec i = parseError ("Illegal precedence: " ++ show i)
-- Stolen from Hugs' Prelude
readInteger :: String -> Integer
readInteger ('0':'o':ds) = readInteger2 8 isOctDigit ds
readInteger ('0':'x':ds) = readInteger2 16 isHexDigit ds
readInteger ds = readInteger2 10 isDigit ds
readInteger2 :: Integer -> (Char -> Bool) -> String -> Integer
readInteger2 radix isDig ds
= foldl1 (\n d -> n * radix + d) (map (fromIntegral . digitToInt) ds)
-- Hack...
readRational :: String -> Rational
readRational xs = (readInteger (i++m))%1 * 10^^(case e of {[] -> 0; ('+':e2) -> read e2; _ -> read e} - length m)
where (i,r1) = span isDigit xs
(m,r2) = span isDigit (dropWhile (=='.') r1)
e = dropWhile (=='e') r2
mkRecConstrOrUpdate :: HsExp -> [HsFieldUpdate] -> P HsExp
mkRecConstrOrUpdate (HsCon c) fs = returnP (HsRecConstr c fs)
mkRecConstrOrUpdate exp fs@(_:_) = returnP (HsRecUpdate exp fs)
mkRecConstrOrUpdate _ _ = parseError "Empty record update"
\end{code}
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