module Language.Egison.Desugar
(
DesugarM
, runDesugarM
, desugarTopExpr
, desugar
) where
import Control.Applicative (Applicative)
import Control.Applicative ((<$>), (<*>), (<*), (*>), pure)
import qualified Data.Sequence as Sq
import Data.Sequence (ViewL(..), (<|))
import qualified Data.Set as S
import Data.Set (Set)
import Data.Char (toUpper)
import Control.Monad.Error
import Control.Monad.State
import Control.Monad.Reader
import Control.Monad.Identity
import Language.Egison.Types
type Subst = [(String, EgisonExpr)]
newtype DesugarM a = DesugarM { unDesugarM :: ReaderT Subst (ErrorT EgisonError Fresh) a }
deriving (Functor, Applicative, Monad, MonadError EgisonError, MonadFresh, MonadReader Subst)
runDesugarM :: DesugarM a -> Fresh (Either EgisonError a)
runDesugarM = runErrorT . flip runReaderT [] . unDesugarM
desugarTopExpr :: EgisonTopExpr -> DesugarM EgisonTopExpr
desugarTopExpr (Define name expr) = do
expr' <- desugar expr
return (Define name expr')
desugarTopExpr (Test expr) = do
expr' <- desugar expr
return (Test expr')
desugarTopExpr expr = return expr
desugar :: EgisonExpr -> DesugarM EgisonExpr
desugar (AlgebraicDataMatcherExpr patterns) = do
matcherName <- fresh
matcherRef <- return $ VarExpr matcherName
matcher <- genMatcherClauses patterns matcherRef
return $ LetRecExpr [([matcherName], matcher)] matcherRef
where
genMatcherClauses :: [(String, [EgisonExpr])] -> EgisonExpr -> DesugarM EgisonExpr
genMatcherClauses patterns matcher = do
main <- genMainClause patterns matcher
body <- mapM genMatcherClause patterns
footer <- genSomethingClause
clauses <- return $ [main] ++ body ++ [footer]
return $ MatcherExpr clauses
genMainClause :: [(String, [EgisonExpr])] -> EgisonExpr -> DesugarM (PrimitivePatPattern, EgisonExpr, [(PrimitiveDataPattern, EgisonExpr)])
genMainClause patterns matcher = do
clauses <- genClauses patterns
return (PPValuePat "val", TupleExpr []
,[(PDPatVar "tgt", (MatchExpr (TupleExpr [(VarExpr "val"), (VarExpr "tgt")])
(TupleExpr [matcher, matcher])
clauses))])
where
genClauses :: [(String, [EgisonExpr])] -> DesugarM [MatchClause]
genClauses patterns = (++) <$> mapM genClause patterns
<*> pure [((TuplePat [WildCard, WildCard]), matchingFailure)]
genClause :: (String, [EgisonExpr]) -> DesugarM MatchClause
genClause pattern = do
(pat0, pat1) <- genMatchingPattern pattern
return (TuplePat [pat0, pat1], matchingSuccess)
genMatchingPattern :: (String, [EgisonExpr]) -> DesugarM (EgisonPattern, EgisonPattern)
genMatchingPattern (name, patterns) = do
names <- mapM (const fresh) patterns
return $ ((InductivePat name (map PatVar names))
,(InductivePat name (map (ValuePat . VarExpr) names)))
genMatcherClause :: (String, [EgisonExpr]) -> DesugarM (PrimitivePatPattern, EgisonExpr, [(PrimitiveDataPattern, EgisonExpr)])
genMatcherClause pattern = do
(ppat, matchers) <- genPrimitivePatPat pattern
(dpat, body) <- genPrimitiveDataPat pattern
return (ppat, TupleExpr matchers, [(dpat, CollectionExpr (Sq.singleton . ElementExpr . TupleExpr $ body)), (PDWildCard, matchingFailure)])
where
genPrimitivePatPat :: (String, [EgisonExpr]) -> DesugarM (PrimitivePatPattern, [EgisonExpr])
genPrimitivePatPat (name, matchers) = do
patterns' <- mapM (const $ return PPPatVar) matchers
return (PPInductivePat name patterns', matchers)
genPrimitiveDataPat :: (String, [EgisonExpr]) -> DesugarM (PrimitiveDataPattern, [EgisonExpr])
genPrimitiveDataPat (name, patterns) = do
patterns' <- mapM (const fresh) patterns
return (PDInductivePat (capitalize name) $ map PDPatVar patterns', map VarExpr patterns')
capitalize :: String -> String
capitalize (x:xs) = toUpper x : xs
genSomethingClause :: DesugarM (PrimitivePatPattern, EgisonExpr, [(PrimitiveDataPattern, EgisonExpr)])
genSomethingClause =
return (PPPatVar, (TupleExpr [SomethingExpr]), [(PDPatVar "tgt", CollectionExpr . Sq.singleton $ ElementExpr (VarExpr "tgt"))])
matchingSuccess :: EgisonExpr
matchingSuccess = CollectionExpr . Sq.singleton. ElementExpr $ TupleExpr []
matchingFailure :: EgisonExpr
matchingFailure = CollectionExpr Sq.empty
desugar (MatchLambdaExpr matcher clauses) = do
name <- fresh
matcher' <- desugar matcher
clauses' <- desugarMatchClauses clauses
return $ LambdaExpr [name] (MatchExpr (VarExpr name) matcher' clauses')
desugar (ArrayRefExpr expr nums) =
case nums of
(TupleExpr nums') -> desugar $ IndexedExpr expr nums'
_ -> desugar $ IndexedExpr expr [nums]
desugar (IndexedExpr expr indices) =
IndexedExpr <$> desugar expr <*> (mapM desugar indices)
desugar (InductiveDataExpr name exprs) = do
exprs' <- mapM desugar exprs
return $ InductiveDataExpr name exprs'
desugar (TupleExpr exprs) = do
exprs' <- mapM desugar exprs
return $ TupleExpr exprs'
desugar expr@(CollectionExpr seq) =
case Sq.viewl seq of
EmptyL -> return expr
ElementExpr seqHead :< seqTail -> do
seqHead' <- desugar seqHead
(CollectionExpr seqTail') <- desugar (CollectionExpr seqTail)
return $ CollectionExpr (ElementExpr seqHead' <| seqTail')
SubCollectionExpr seqHead :< seqTail -> do
seqHead' <- desugar seqHead
(CollectionExpr seqTail') <- desugar (CollectionExpr seqTail)
return $ CollectionExpr (SubCollectionExpr seqHead' <| seqTail')
desugar (LambdaExpr names expr) = do
expr' <- desugar expr
return $ LambdaExpr names expr'
desugar (PatternFunctionExpr names pattern) = do
pattern' <- desugarPattern pattern
return $ PatternFunctionExpr names pattern'
desugar (IfExpr expr0 expr1 expr2) = do
expr0' <- desugar expr0
expr1' <- desugar expr1
expr2' <- desugar expr2
return $ IfExpr expr0' expr1' expr2'
desugar (LetExpr binds expr) = do
binds' <- desugarBindings binds
expr' <- desugar expr
return $ LetExpr binds' expr'
desugar (LetRecExpr binds expr) = do
binds' <- desugarBindings binds
expr' <- desugar expr
return $ LetRecExpr binds' expr'
desugar (MatchExpr expr0 expr1 clauses) = do
expr0' <- desugar expr0
expr1' <- desugar expr1
clauses' <- desugarMatchClauses clauses
return (MatchExpr expr0' expr1' clauses')
desugar (MatchAllExpr expr0 expr1 clause) = do
expr0' <- desugar expr0
expr1' <- desugar expr1
clause' <- desugarMatchClause clause
return $ MatchAllExpr expr0' expr1' clause'
desugar (DoExpr binds expr) = do
binds' <- desugarBindings binds
expr' <- desugar expr
return $ DoExpr binds' expr'
desugar (ApplyExpr expr0 expr1) = do
expr0' <- desugar expr0
expr1' <- desugar expr1
return $ ApplyExpr expr0' expr1'
desugar (VarExpr name) = do
asks $ maybe (VarExpr name) id . lookup name
desugar expr = return expr
desugarPattern :: EgisonPattern -> DesugarM EgisonPattern
desugarPattern pattern = LetPat (map makeBinding $ S.elems $ collectName pattern) <$> desugarPattern' pattern
where
collectNames :: [EgisonPattern] -> Set String
collectNames patterns = S.unions $ map collectName patterns
collectName :: EgisonPattern -> Set String
collectName (NotPat pattern) = collectName pattern
collectName (AndPat patterns) = collectNames patterns
collectName (TuplePat patterns) = collectNames patterns
collectName (InductivePat _ patterns) = collectNames patterns
collectName (ApplyPat _ patterns) = collectNames patterns
collectName (LoopPat _ _ pattern1 pattern2) = collectName pattern1 `S.union` collectName pattern2
collectName (LetPat _ pattern) = collectName pattern
collectName (IndexedPat (PatVar name) _) = S.singleton name
collectName (OrPat patterns) = collectNames patterns
collectName _ = S.empty
makeBinding :: String -> BindingExpr
makeBinding name = ([name], ArrayExpr [])
desugarPattern' :: EgisonPattern -> DesugarM EgisonPattern
desugarPattern' (ValuePat expr) = ValuePat <$> desugar expr
desugarPattern' (PredPat expr) = PredPat <$> desugar expr
desugarPattern' (NotPat pattern) = NotPat <$> desugarPattern' pattern
desugarPattern' (AndPat patterns) = AndPat <$> mapM desugarPattern' patterns
desugarPattern' (TuplePat patterns) = TuplePat <$> mapM desugarPattern' patterns
desugarPattern' (InductivePat name patterns) =
InductivePat name <$> mapM desugarPattern' patterns
desugarPattern' (IndexedPat pattern exprs) =
IndexedPat <$> desugarPattern' pattern <*> mapM desugar exprs
desugarPattern' (ApplyPat expr patterns) =
ApplyPat <$> desugar expr <*> mapM desugarPattern' patterns
desugarPattern' (LoopPat name range pattern1 pattern2) =
LoopPat name <$> desugarLoopRange range <*> desugarPattern' pattern1 <*> desugarPattern' pattern2
desugarPattern' (LetPat binds pattern) = do
LetPat <$> desugarBindings binds <*> desugarPattern' pattern
desugarPattern' (OrPat patterns) =
OrPat <$> mapM desugarPattern' patterns
desugarPattern' pattern = return pattern
desugarLoopRange :: LoopRange -> DesugarM LoopRange
desugarLoopRange (LoopRangeConstant expr1 expr2) = do
expr1' <- desugar expr1
expr2' <- desugar expr2
return $ LoopRangeConstant expr1' expr2'
desugarLoopRange (LoopRangeVariable expr1 name) = do
expr1' <- desugar expr1
return $ LoopRangeVariable expr1' name
desugarBinding :: BindingExpr -> DesugarM BindingExpr
desugarBinding (name, expr) = do
expr' <- desugar expr
return $ (name, expr')
desugarBindings :: [BindingExpr] -> DesugarM [BindingExpr]
desugarBindings (bind:rest) = do
bind' <- desugarBinding bind
rest' <- desugarBindings rest
return $ bind' : rest'
desugarBindings [] = return []
desugarMatchClause :: MatchClause -> DesugarM MatchClause
desugarMatchClause (pattern, expr) = do
pattern' <- desugarPattern pattern
expr' <- desugar expr
return $ (pattern', expr')
desugarMatchClauses :: [MatchClause] -> DesugarM [MatchClause]
desugarMatchClauses (clause:rest) = do
clause' <- desugarMatchClause clause
rest' <- desugarMatchClauses rest
return $ clause' : rest'
desugarMatchClauses [] = return []