ddc-core-0.3.1.1: DDC/Core/Parser/Exp.hs
-- | Core language parser.
module DDC.Core.Parser.Exp
( pExp
, pExpApp
, pExpAtom
, pLets
, pType
, pTypeApp
, pTypeAtom)
where
import DDC.Core.Exp
import DDC.Core.Parser.Witness
import DDC.Core.Parser.Param
import DDC.Core.Parser.Type
import DDC.Core.Parser.Base
import DDC.Core.Lexer.Tokens
import DDC.Core.Compounds
import DDC.Base.Parser ((<?>))
import qualified DDC.Base.Parser as P
import qualified DDC.Type.Compounds as T
import Control.Monad.Error
-- Expressions ----------------------------------------------------------------
-- | Parse a core language expression.
pExp :: Ord n => Parser n (Exp () n)
pExp
= P.choice
-- Level-0 lambda abstractions
-- \(x1 x2 ... : TYPE) (y1 y2 ... : TYPE) ... . EXP
[ do pTok KBackSlash
bs <- liftM concat
$ P.many1
$ do pTok KRoundBra
bs' <- P.many1 pBinder
pTok KColon
t <- pType
pTok KRoundKet
return (map (\b -> T.makeBindFromBinder b t) bs')
pTok KDot
xBody <- pExp
return $ foldr (XLam ()) xBody bs
-- Level-1 lambda abstractions.
-- /\(x1 x2 ... : TYPE) (y1 y2 ... : TYPE) ... . EXP
, do pTok KBigLambda
bs <- liftM concat
$ P.many1
$ do pTok KRoundBra
bs' <- P.many1 pBinder
pTok KColon
t <- pType
pTok KRoundKet
return (map (\b -> T.makeBindFromBinder b t) bs')
pTok KDot
xBody <- pExp
return $ foldr (XLAM ()) xBody bs
-- let expression
, do lts <- pLets
pTok KIn
x2 <- pExp
return $ XLet () lts x2
-- do { STMTS }
-- Sugar for a let-expression.
, do pTok KDo
pTok KBraceBra
xx <- pStmts
pTok KBraceKet
return $ xx
-- withregion CON in EXP
, do pTok KWithRegion
u <- P.choice
[ do n <- pVar
return $ UName n
, do n <- pCon
return $ UPrim n kRegion]
pTok KIn
x <- pExp
return $ XLet () (LWithRegion u) x
-- case EXP of { ALTS }
, do pTok KCase
x <- pExp
pTok KOf
pTok KBraceBra
alts <- P.sepEndBy1 pAlt (pTok KSemiColon)
pTok KBraceKet
return $ XCase () x alts
-- match PAT <- EXP else EXP in EXP
-- Sugar for a case-expression.
, do pTok KMatch
p <- pPat
pTok KArrowDashLeft
x1 <- pExp
pTok KElse
x2 <- pExp
pTok KIn
x3 <- pExp
return $ XCase () x1 [AAlt p x3, AAlt PDefault x2]
-- weakeff [TYPE] in EXP
, do pTok KWeakEff
pTok KSquareBra
t <- pType
pTok KSquareKet
pTok KIn
x <- pExp
return $ XCast () (CastWeakenEffect t) x
-- weakclo {EXP;+} in EXP
, do pTok KWeakClo
pTok KBraceBra
xs <- liftM concat $ P.sepEndBy1 pArgs (pTok KSemiColon)
pTok KBraceKet
pTok KIn
x <- pExp
return $ XCast () (CastWeakenClosure xs) x
-- purify <WITNESS> in EXP
, do pTok KPurify
pTok KAngleBra
w <- pWitness
pTok KAngleKet
pTok KIn
x <- pExp
return $ XCast () (CastPurify w) x
-- forget <WITNESS> in EXP
, do pTok KForget
pTok KAngleBra
w <- pWitness
pTok KAngleKet
pTok KIn
x <- pExp
return $ XCast () (CastForget w) x
-- APP
, do pExpApp
]
<?> "an expression"
-- Applications.
pExpApp :: Ord n => Parser n (Exp () n)
pExpApp
= do x1 <- pExpAtom
P.choice
[ do xs <- liftM concat $ P.many1 pArgs
return $ foldl (XApp ()) x1 xs
, return x1]
<?> "an expression or application"
-- Comp, Witness or Spec arguments.
pArgs :: Ord n => Parser n [Exp () n]
pArgs
= P.choice
-- [TYPE]
[ do pTok KSquareBra
t <- pType
pTok KSquareKet
return [XType t]
-- [: TYPE0 TYPE0 ... :]
, do pTok KSquareColonBra
ts <- P.many1 pTypeAtom
pTok KSquareColonKet
return $ map XType ts
-- <WITNESS>
, do pTok KAngleBra
w <- pWitness
pTok KAngleKet
return [XWitness w]
-- <: WITNESS0 WITNESS0 ... :>
, do pTok KAngleColonBra
ws <- P.many1 pWitnessAtom
pTok KAngleColonKet
return $ map XWitness ws
-- EXP0
, do x <- pExpAtom
return [x]
]
<?> "a type, witness or expression argument"
-- | Parse a variable, constructor or parenthesised expression.
pExpAtom :: Ord n => Parser n (Exp () n)
pExpAtom
= P.choice
-- (EXP2)
[ do pTok KRoundBra
t <- pExp
pTok KRoundKet
return $ t
-- The unit data constructor.
, do pTok KDaConUnit
return $ XCon () dcUnit
-- Named algebraic constructors.
-- We just fill-in the type with tBot for now, and leave it to
-- the spreader to attach the real type.
, do con <- pCon
return $ XCon () (mkDaConAlg con (T.tBot T.kData))
-- Literals.
-- We just fill-in the type with tBot for now, and leave it to
-- the spreader to attach the real type.
-- We also set the literal as being algebraic, which may not be
-- true (as for Floats). The spreader also needs to fix this.
, do lit <- pLit
return $ XCon () (mkDaConAlg lit (T.tBot T.kData))
-- Debruijn indices
, do i <- pIndex
return $ XVar () (UIx i)
-- Variables
, do var <- pVar
return $ XVar () (UName var)
]
<?> "a variable, constructor, or parenthesised type"
-- Alternatives ---------------------------------------------------------------
-- Case alternatives.
pAlt :: Ord n => Parser n (Alt () n)
pAlt
= do p <- pPat
pTok KArrowDash
x <- pExp
return $ AAlt p x
-- Patterns.
pPat :: Ord n => Parser n (Pat n)
pPat
= P.choice
[ -- Wildcard
do pTok KUnderscore
return $ PDefault
-- LIT
, do nLit <- pLit
return $ PData (mkDaConAlg nLit (T.tBot T.kData)) []
-- Unit
, do pTok KDaConUnit
return $ PData dcUnit []
-- CON BIND BIND ...
, do nCon <- pCon
bs <- P.many pBindPat
return $ PData (mkDaConAlg nCon (T.tBot T.kData)) bs]
-- Binds in patterns can have no type annotation,
-- or can have an annotation if the whole thing is in parens.
pBindPat :: Ord n => Parser n (Bind n)
pBindPat
= P.choice
-- Plain binder.
[ do b <- pBinder
return $ T.makeBindFromBinder b (T.tBot T.kData)
-- Binder with type, wrapped in parens.
, do pTok KRoundBra
b <- pBinder
pTok KColon
t <- pType
pTok KRoundKet
return $ T.makeBindFromBinder b t
]
-- Bindings -------------------------------------------------------------------
pLets :: Ord n => Parser n (Lets () n)
pLets
= P.choice
[ -- non-recursive let.
do pTok KLet
(mode1, b1, x1) <- pLetBinding
return $ LLet mode1 b1 x1
-- recursive let.
, do pTok KLetRec
P.choice
-- Multiple bindings in braces
[ do pTok KBraceBra
lets <- P.sepEndBy1 pLetRecBinding (pTok KSemiColon)
pTok KBraceKet
return $ LRec lets
-- A single binding without braces.
, do ll <- pLetRecBinding
return $ LRec [ll]
]
-- Local region binding.
-- letregions [BINDER] with { BINDER : TYPE ... } in EXP
-- letregions [BINDER] in EXP
, do pTok KLetRegions
brs <- P.manyTill pBinder (P.try $ P.lookAhead $ P.choice [pTok KIn, pTok KWith])
let bs = map (flip T.makeBindFromBinder T.kRegion) brs
pLetWits bs
, do pTok KLetRegion
br <- pBinder
let b = T.makeBindFromBinder br T.kRegion
pLetWits [b]
]
pLetWits :: Ord n => [Bind n] -> Parser n (Lets () n)
pLetWits bs
= P.choice
[ do pTok KWith
pTok KBraceBra
wits <- P.sepBy
(do b <- pBinder
pTok KColon
t <- pTypeApp
return $ T.makeBindFromBinder b t)
(pTok KSemiColon)
pTok KBraceKet
return (LLetRegions bs wits)
, do return (LLetRegions bs [])
]
-- | A binding for let expression.
pLetBinding :: Ord n => Parser n (LetMode n, Bind n, Exp () n)
pLetBinding
= do b <- pBinder
P.choice
[ do -- Binding with full type signature.
-- BINDER : TYPE = EXP
pTok KColon
t <- pType
mode <- pLetMode
pTok KEquals
xBody <- pExp
return $ (mode, T.makeBindFromBinder b t, xBody)
, do -- Non-function binding with no type signature.
-- This form can't be used with letrec as we can't use it
-- to build the full type sig for the let-bound variable.
-- BINDER = EXP
mode <- pLetMode
pTok KEquals
xBody <- pExp
let t = T.tBot T.kData
return $ (mode, T.makeBindFromBinder b t, xBody)
, do -- Binding using function syntax.
ps <- liftM concat
$ P.many pBindParamSpec
P.choice
[ do -- Function syntax with a return type.
-- We can make the full type sig for the let-bound variable.
-- BINDER PARAM1 PARAM2 .. PARAMN : TYPE = EXP
pTok KColon
tBody <- pType
mode <- pLetMode
pTok KEquals
xBody <- pExp
let x = expOfParams () ps xBody
let t = funTypeOfParams ps tBody
return (mode, T.makeBindFromBinder b t, x)
-- Function syntax with no return type.
-- We can't make the type sig for the let-bound variable,
-- but we can create lambda abstractions with the given
-- parameter types.
-- BINDER PARAM1 PARAM2 .. PARAMN = EXP
, do mode <- pLetMode
pTok KEquals
xBody <- pExp
let x = expOfParams () ps xBody
let t = T.tBot T.kData
return (mode, T.makeBindFromBinder b t, x) ]
]
-- | Parse a let mode specifier.
-- Only allow the lazy specifier with non-recursive bindings.
-- We don't support value recursion, so the right of all recursive
-- bindings must be explicit lambda abstractions anyway, so there's
-- no point suspending them.
pLetMode :: Ord n => Parser n (LetMode n)
pLetMode
= do P.choice
-- lazy <WITNESS>
[ do pTok KLazy
P.choice
[ do pTok KAngleBra
w <- pWitness
pTok KAngleKet
return $ LetLazy (Just w)
, do return $ LetLazy Nothing ]
, do return $ LetStrict ]
-- | Letrec bindings must have a full type signature,
-- or use function syntax with a return type so that we can make one.
pLetRecBinding :: Ord n => Parser n (Bind n, Exp () n)
pLetRecBinding
= do b <- pBinder
P.choice
[ do -- Binding with full type signature.
-- BINDER : TYPE = EXP
pTok KColon
t <- pType
pTok KEquals
xBody <- pExp
return $ (T.makeBindFromBinder b t, xBody)
, do -- Binding using function syntax.
-- BINDER PARAM1 PARAM2 .. PARAMN : TYPE = EXP
ps <- liftM concat
$ P.many pBindParamSpec
pTok KColon
tBody <- pType
let t = funTypeOfParams ps tBody
pTok KEquals
xBody <- pExp
let x = expOfParams () ps xBody
return (T.makeBindFromBinder b t, x) ]
-- Statements -----------------------------------------------------------------
data Stmt n
= StmtBind (Bind n) (Exp () n)
| StmtMatch (Pat n) (Exp () n) (Exp () n)
| StmtNone (Exp () n)
-- | Parse a single statement.
pStmt :: Ord n => Parser n (Stmt n)
pStmt
= P.choice
[ -- BINDER = EXP ;
-- We need the 'try' because a VARIABLE binders can also be parsed
-- as a function name in a non-binding statement.
--
P.try $
do br <- pBinder
pTok KEquals
x1 <- pExp
let t = T.tBot T.kData
let b = T.makeBindFromBinder br t
return $ StmtBind b x1
-- PAT <- EXP else EXP;
-- Sugar for a case-expression.
-- We need the 'try' because the PAT can also be parsed
-- as a function name in a non-binding statement.
, P.try $
do p <- pPat
pTok KArrowDashLeft
x1 <- pExp
pTok KElse
x2 <- pExp
return $ StmtMatch p x1 x2
-- EXP
, do x <- pExp
return $ StmtNone x
]
-- | Parse some statements.
pStmts :: Ord n => Parser n (Exp () n)
pStmts
= do stmts <- P.sepEndBy1 pStmt (pTok KSemiColon)
case makeStmts stmts of
Nothing -> P.unexpected "do-block must end with a statement"
Just x -> return x
-- | Make an expression from some statements.
makeStmts :: [Stmt n] -> Maybe (Exp () n)
makeStmts ss
= case ss of
[StmtNone x]
-> Just x
StmtNone x1 : rest
| Just x2 <- makeStmts rest
-> Just $ XLet () (LLet LetStrict (BNone (T.tBot T.kData)) x1) x2
StmtBind b x1 : rest
| Just x2 <- makeStmts rest
-> Just $ XLet () (LLet LetStrict b x1) x2
StmtMatch p x1 x2 : rest
| Just x3 <- makeStmts rest
-> Just $ XCase () x1
[ AAlt p x3
, AAlt PDefault x2]
_ -> Nothing