90 lines
No EOL
3.1 KiB
Haskell
90 lines
No EOL
3.1 KiB
Haskell
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module Cases (caseToMatch, Match (..), Clause (..), matchSubst) where
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import Control.Arrow (first)
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import Control.Monad (liftM,foldM)
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import Data.List (groupBy,sortBy,lookup)
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import Data.Maybe (fromMaybe)
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import Ast
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import Located
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import Guid
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import Substitute
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caseToMatch patterns = do
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v <- newVar
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match [v] (map (first (:[])) patterns) Fail
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newVar = do n <- guid
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return $ "case" ++ show n
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data Match = Match String [Clause] Match
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| Break
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| Fail
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| Other CExpr
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| Seq [Match]
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deriving Show
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data Clause = Clause String [String] Match
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deriving Show
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matchSubst :: [(String,String)] -> Match -> Match
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matchSubst _ Break = Break
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matchSubst _ Fail = Fail
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matchSubst pairs (Seq ms) = Seq (map (matchSubst pairs) ms)
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matchSubst pairs (Other (L t s e)) =
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Other . L t s $ foldr ($) e $ map (\(x,y) -> subst x (Var y)) pairs
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matchSubst pairs (Match n cs m) =
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Match (varSubst n) (map clauseSubst cs) (matchSubst pairs m)
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where varSubst v = fromMaybe v (lookup v pairs)
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clauseSubst (Clause c vs m) =
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Clause c (map varSubst vs) (matchSubst pairs m)
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isCon (PData _ _ : _, _) = True
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isCon _ = False
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isVar p = not (isCon p)
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match :: [String] -> [([Pattern],CExpr)] -> Match -> GuidCounter Match
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match [] [] def = return def
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match [] [([],e)] Fail = return $ Other e
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match [] [([],e)] Break = return $ Other e
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match [] cs def = return $ Seq (map (Other . snd) cs ++ [def])
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match vs cs def
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| all isVar cs = matchVar vs cs def
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| all isCon cs = matchCon vs cs def
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| otherwise = matchMix vs cs def
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matchVar :: [String] -> [([Pattern],CExpr)] -> Match -> GuidCounter Match
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matchVar (v:vs) cs def = match vs (map subVar cs) def
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where
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subVar (p:ps, ce@(L t s e)) =
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let
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loc = L t s
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subOnePattern (PVar x) = subst x (Var v) e
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subOnePattern (PAsVar x p) =
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subst x (Var v) e
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subOnePattern PAnything = e
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subOnePattern (PRecord fs) =
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foldr (\x -> subst x (Access (loc (Var v)) x)) e fs
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in
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(ps, L t s $ subOnePattern p)
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matchCon :: [String] -> [([Pattern],CExpr)] -> Match -> GuidCounter Match
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matchCon (v:vs) cs def = (flip (Match v) def) `liftM` mapM toClause css
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where css = groupBy (withName (==)) $ sortBy (withName compare) cs
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withName f (PData n1 _:_,_) (PData n2 _:_,_) = f n1 n2
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toClause cs = let (PData name _ : _ , _) = head cs in
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matchClause name (v:vs) cs Break
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matchClause :: String -> [String] -> [([Pattern],CExpr)] -> Match -> GuidCounter Clause
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matchClause c (v:vs) cs def =
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do vs' <- getVars
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Clause c vs' `liftM` match (vs' ++ vs) (map flatten cs) def
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where flatten (PData _ ps' : ps, e) = (ps' ++ ps, e)
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getVars = let (PData _ ps : _, _) = head cs in
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mapM (\_ -> newVar) ps
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matchMix :: [String] -> [([Pattern],CExpr)] -> Match -> GuidCounter Match
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matchMix vs cs def = foldM (flip $ match vs) def (reverse css)
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where css = groupBy (\p1 p2 -> isCon p1 == isCon p2) cs |