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
6import Control.Monad.State
7import Debug.Trace
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 :: Bool -> [(Term, Term)] -> CaseDef
27simpleCase tc [] = CaseDef [] (UnmatchedCase "No pattern clauses")
28simpleCase tc cs = let pats = map (\ (l, r) -> (toPats tc 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
40-- If there are repeated variables, take the *last* one (could be name shadowing
41-- in a where clause, so take the most recent).
43toPats :: Bool -> Term -> [Pat]
44toPats tc f = reverse (toPat tc (getArgs f)) where
45 getArgs (App f a) = a : getArgs f
46 getArgs _ = []
48toPat :: Bool -> [Term] -> [Pat]
49toPat tc tms = evalState (mapM (\x -> toPat' x []) tms) []
50 where
51 toPat' (P (DCon t a) n _) args = do args' <- mapM (\x -> toPat' x []) args
52 return $ PCon n t args'
53 -- Typecase
54 toPat' (P (TCon t a) n _) args | tc
55 = do args' <- mapM (\x -> toPat' x []) args
56 return $ PCon n t args'
57 toPat' (Constant IType) [] | tc = return $ PCon (UN ["Int"]) 1 []
58 toPat' (Constant FlType) [] | tc = return $ PCon (UN ["Float"]) 2 []
59 toPat' (Constant ChType) [] | tc = return $ PCon (UN ["Char"]) 3 []
60 toPat' (Constant StrType) [] | tc = return $ PCon (UN ["String"]) 4 []
61 toPat' (Constant PtrType) [] | tc = return $ PCon (UN ["Ptr"]) 5 []
63 toPat' (P Bound n _) [] = do ns <- get
64 if n `elem` ns
65 then return PAny
66 else do put (n : ns)
67 return (PV n)
68 toPat' (App f a) args = toPat' f (a : args)
69 toPat' (Constant c) args
70 | isType c = return PAny
71 | otherwise = return $ PConst c
72 toPat' _ _ = return PAny
74 isType (I _) = False
75 isType (Fl _) = False
76 isType (Str _) = False
77 isType (Ch _) = False
78 isType _ = True
80data Partition = Cons [Clause]
81 | Vars [Clause]
83isVarPat (PV _ : ps , _) = True
84isVarPat (PAny : ps , _) = True
85isVarPat _ = False
87isConPat (PCon _ _ _ : ps, _) = True
88isConPat (PConst _ : ps, _) = True
89isConPat _ = False
91partition :: [Clause] -> [Partition]
92partition [] = []
93partition ms@(m : _)
94 | isVarPat m = let (vars, rest) = span isVarPat ms in
95 Vars vars : partition rest
96 | isConPat m = let (cons, rest) = span isConPat ms in
97 Cons cons : partition rest
98partition xs = error $ "Partition " ++ show xs
100match :: [Name] -> [Clause] -> SC -- error case
101 -> State CS SC
102match [] (([], ret) : _) err = return $ STerm ret -- run out of arguments
103match vs cs err = mixture vs (partition cs) err
105mixture :: [Name] -> [Partition] -> SC -> State CS SC
106mixture vs [] err = return err
107mixture vs (Cons ms : ps) err = do fallthrough <- mixture vs ps err
108 conRule vs ms fallthrough
109mixture vs (Vars ms : ps) err = do fallthrough <- mixture vs ps err
110 varRule vs ms fallthrough
112data ConType = CName Name Int -- named constructor
113 | CConst Const -- constant, not implemented yet
115data Group = ConGroup ConType -- Constructor
116 [([Pat], Clause)] -- arguments and rest of alternative
118conRule :: [Name] -> [Clause] -> SC -> State CS SC
119conRule (v:vs) cs err = do groups <- groupCons cs
120 caseGroups (v:vs) groups err
122caseGroups :: [Name] -> [Group] -> SC -> State CS SC
123caseGroups (v:vs) gs err = do g <- altGroups gs
124 return $ Case v g
125 where
126 altGroups [] = return [DefaultCase err]
127 altGroups (ConGroup (CName n i) args : cs)
128 = do g <- altGroup n i args
129 rest <- altGroups cs
130 return (g : rest)
131 altGroups (ConGroup (CConst c) args : cs)
132 = do g <- altConstGroup c args
133 rest <- altGroups cs
134 return (g : rest)
136 altGroup n i gs = do (newArgs, nextCs) <- argsToAlt gs
137 matchCs <- match (newArgs ++ vs) nextCs err
138 return $ ConCase n i newArgs matchCs
139 altConstGroup n gs = do (_, nextCs) <- argsToAlt gs
140 matchCs <- match vs nextCs err
141 return $ ConstCase n matchCs
143argsToAlt :: [([Pat], Clause)] -> State CS ([Name], [Clause])
144argsToAlt [] = return ([], [])
145argsToAlt rs@((r, m) : _)
146 = do newArgs <- getNewVars r
147 return (newArgs, addRs rs)
148 where
149 getNewVars [] = return []
150 getNewVars ((PV n) : ns) = do nsv <- getNewVars ns
151 return (n : nsv)
152 getNewVars (_ : ns) = do v <- getVar
153 nsv <- getNewVars ns
154 return (v : nsv)
155 addRs [] = []
156 addRs ((r, (ps, res)) : rs) = ((r++ps, res) : addRs rs)
158getVar :: State CS Name
159getVar = do v <- get; put (v+1); return (MN v "e")
161groupCons :: [Clause] -> State CS [Group]
162groupCons cs = gc [] cs
163 where
164 gc acc [] = return acc
165 gc acc ((p : ps, res) : cs) =
166 do acc' <- addGroup p ps res acc
167 gc acc' cs
168 addGroup p ps res acc = case p of
169 PCon con i args -> return $ addg con i args (ps, res) acc
170 PConst cval -> return $ addConG cval (ps, res) acc
171 pat -> fail $ show pat ++ " is not a constructor or constant (can't happen)"
173 addg con i conargs res [] = [ConGroup (CName con i) [(conargs, res)]]
174 addg con i conargs res (g@(ConGroup (CName n j) cs):gs)
175 | i == j = ConGroup (CName n i) (cs ++ [(conargs, res)]) : gs
176 | otherwise = g : addg con i conargs res gs
178 addConG con res [] = [ConGroup (CConst con) [([], res)]]
179 addConG con res (g@(ConGroup (CConst n) cs) : gs)
180 | con == n = ConGroup (CConst n) (cs ++ [([], res)]) : gs
181 | otherwise = g : addConG con res gs
183varRule :: [Name] -> [Clause] -> SC -> State CS SC
184varRule (v : vs) alts err =
185 do let alts' = map (repVar v) alts
186 match vs alts' err
187 where
188 repVar v (PV p : ps , res) = (ps, subst p (P Bound v undefined) res)
189 repVar v (PAny : ps , res) = (ps, res)
191{-
192mkOperator :: CaseDef -> [Value] -> Maybe Value
193mkOperator (CaseDef ns casetree) args
194 | length args /= length ns = Nothing
195 | otherwise = evalArgs (zip ns args) casetree
196 where
197 evalArgs map (Case n alts) =
198 do v <- lookup n map
199 (altmap, tm) <- findAlt (getValArgs v) alts map
200 evalArgs altmap tm
201 evalArgs map (STerm tm) =
202 evalArgs map (UnmatchedCase _) = Nothing
204 getValArgs tm = getValArgs' tm []
205 getValArgs' (VApp f a) as = getValArgs' f (a:as)
206 getValArgs' f as = (f, as)
208-}