git.iko.soy/Idris-dev
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Idris-dev/src/Core/CaseTree.hs
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1module Core.CaseTree(CaseDef(..), SC(..), CaseAlt(..), CaseTree,
2 simpleCase) where
4import Core.TT
5-- import Core.Evaluate
7import Control.Monad.State
9data CaseDef = CaseDef [Name] SC
10 deriving Show
12data SC = Case Name [CaseAlt]
13 | STerm Term
14 | UnmatchedCase String -- error message
15 deriving Show
17data CaseAlt = ConCase Name Int [Name] SC
18 | ConstCase Const SC
19 | DefaultCase SC
20 deriving Show
22type CaseTree = SC
23type Clause = ([Pat], Term)
24type CS = Int
26simpleCase :: [(Term, Term)] -> CaseDef
27simpleCase [] = CaseDef [] (UnmatchedCase "No pattern clauses")
28simpleCase cs = let pats = map (\ (l, r) -> (toPats l, r)) cs
29 numargs = length (fst (head pats))
30 ns = take numargs args in
31 CaseDef ns (evalState (match ns pats (UnmatchedCase "Error")) numargs)
32 where args = map (\i -> MN i "e") [0..]
34data Pat = PCon Name Int [Pat]
35 | PConst Const
36 | PV Name
37 | PAny
38 deriving Show
40toPats :: Term -> [Pat]
41toPats f = map toPat (reverse (getArgs f)) where
42 getArgs (App f a) = a : getArgs f
43 getArgs _ = []
45toPat :: Term -> Pat
46toPat tm = evalState (toPat' tm []) []
47 where
48 toPat' (P (DCon t a) n _) args = return $ PCon n t args
49 toPat' (P Bound n _) [] = do ns <- get
50 if n `elem` ns
51 then return PAny
52 else return (PV n)
53 toPat' (App f a) args = do a' <- toPat' a []
54 toPat' f (a' : args)
55 toPat' (Constant c) args = return $ PConst c
56 toPat' _ _ = return PAny
58data Partition = Cons [Clause]
59 | Vars [Clause]
61isVarPat (PV _ : ps , _) = True
62isVarPat (PAny : ps , _) = True
63isVarPat _ = False
65isConPat (PCon _ _ _ : ps, _) = True
66isConPat (PConst _ : ps, _) = True
67isConPat _ = False
69partition :: [Clause] -> [Partition]
70partition [] = []
71partition ms@(m : _)
72 | isVarPat m = let (vars, rest) = span isVarPat ms in
73 Vars vars : partition rest
74 | isConPat m = let (cons, rest) = span isConPat ms in
75 Cons cons : partition rest
76partition xs = error $ "Partition " ++ show xs
78match :: [Name] -> [Clause] -> SC -- error case
79 -> State CS SC
80match [] (([], ret) : _) err = return $ STerm ret -- run out of arguments
81match vs cs err = mixture vs (partition cs) err
83mixture :: [Name] -> [Partition] -> SC -> State CS SC
84mixture vs [] err = return err
85mixture vs (Cons ms : ps) err = do fallthrough <- mixture vs ps err
86 conRule vs ms fallthrough
87mixture vs (Vars ms : ps) err = do fallthrough <- mixture vs ps err
88 varRule vs ms fallthrough
90data ConType = CName Name Int -- named constructor
91 | CConst Const -- constant, not implemented yet
93data Group = ConGroup ConType -- Constructor
94 [([Pat], Clause)] -- arguments and rest of alternative
96conRule :: [Name] -> [Clause] -> SC -> State CS SC
97conRule (v:vs) cs err = do groups <- groupCons cs
98 caseGroups (v:vs) groups err
100caseGroups :: [Name] -> [Group] -> SC -> State CS SC
101caseGroups (v:vs) gs err = do g <- altGroups gs
102 return $ Case v g
103 where
104 altGroups [] = return [DefaultCase err]
105 altGroups (ConGroup (CName n i) args : cs)
106 = do g <- altGroup n i args
107 rest <- altGroups cs
108 return (g : rest)
109 altGroups (ConGroup (CConst c) args : cs)
110 = do g <- altConstGroup c args
111 rest <- altGroups cs
112 return (g : rest)
114 altGroup n i gs = do (newArgs, nextCs) <- argsToAlt gs
115 matchCs <- match (newArgs ++ vs) nextCs err
116 return $ ConCase n i newArgs matchCs
117 altConstGroup n gs = do (_, nextCs) <- argsToAlt gs
118 matchCs <- match vs nextCs err
119 return $ ConstCase n matchCs
121argsToAlt :: [([Pat], Clause)] -> State CS ([Name], [Clause])
122argsToAlt [] = return ([], [])
123argsToAlt rs@((r, m) : _)
124 = do newArgs <- getNewVars r
125 return (newArgs, addRs rs)
126 where
127 getNewVars [] = return []
128 getNewVars ((PV n) : ns) = do nsv <- getNewVars ns
129 return (n : nsv)
130 getNewVars (_ : ns) = do v <- getVar
131 nsv <- getNewVars ns
132 return (v : nsv)
133 addRs [] = []
134 addRs ((r, (ps, res)) : rs) = ((r++ps, res) : addRs rs)
136getVar :: State CS Name
137getVar = do v <- get; put (v+1); return (MN v "e")
139groupCons :: [Clause] -> State CS [Group]
140groupCons cs = gc [] cs
141 where
142 gc acc [] = return acc
143 gc acc ((p : ps, res) : cs) =
144 do acc' <- addGroup p ps res acc
145 gc acc' cs
146 addGroup p ps res acc = case p of
147 PCon con i args -> return $ addg con i args (ps, res) acc
148 PConst cval -> return $ addConG cval (ps, res) acc
149 pat -> fail $ show pat ++ " is not a constructor or constant (can't happen)"
151 addg con i conargs res [] = [ConGroup (CName con i) [(conargs, res)]]
152 addg con i conargs res (g@(ConGroup (CName n j) cs):gs)
153 | i == j = ConGroup (CName n i) (cs ++ [(conargs, res)]) : gs
154 | otherwise = g : addg con i conargs res gs
156 addConG con res [] = [ConGroup (CConst con) [([], res)]]
157 addConG con res (g@(ConGroup (CConst n) cs) : gs)
158 | con == n = ConGroup (CConst n) (cs ++ [([], res)]) : gs
159 | otherwise = g : addConG con res gs
161varRule :: [Name] -> [Clause] -> SC -> State CS SC
162varRule (v : vs) alts err =
163 do let alts' = map (repVar v) alts
164 match vs alts' err
165 where
166 repVar v (PV p : ps , res) = (ps, subst p (P Bound v undefined) res)
167 repVar v (PAny : ps , res) = (ps, res)
169{-
170mkOperator :: CaseDef -> [Value] -> Maybe Value
171mkOperator (CaseDef ns casetree) args
172 | length args /= length ns = Nothing
173 | otherwise = evalArgs (zip ns args) casetree
174 where
175 evalArgs map (Case n alts) =
176 do v <- lookup n map
177 (altmap, tm) <- findAlt (getValArgs v) alts map
178 evalArgs altmap tm
179 evalArgs map (STerm tm) =
180 evalArgs map (UnmatchedCase _) = Nothing
182 getValArgs tm = getValArgs' tm []
183 getValArgs' (VApp f a) as = getValArgs' f (a:as)
184 getValArgs' f as = (f, as)
186-}