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, small) 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
26-- simple terms can be inlined trivially - good for primitives in particular
27small :: SC -> Bool
28small (STerm t) = True
29small _ = False
31simpleCase :: Bool -> [(Term, Term)] -> CaseDef
32simpleCase tc [] = CaseDef [] (UnmatchedCase "No pattern clauses")
33simpleCase tc cs = let pats = map (\ (l, r) -> (toPats tc l, r)) cs
34 numargs = length (fst (head pats))
35 ns = take numargs args in
36 CaseDef ns (evalState (match ns pats (UnmatchedCase "Error")) numargs)
37 where args = map (\i -> MN i "e") [0..]
39data Pat = PCon Name Int [Pat]
40 | PConst Const
41 | PV Name
42 | PAny
43 deriving Show
45-- If there are repeated variables, take the *last* one (could be name shadowing
46-- in a where clause, so take the most recent).
48toPats :: Bool -> Term -> [Pat]
49toPats tc f = reverse (toPat tc (getArgs f)) where
50 getArgs (App f a) = a : getArgs f
51 getArgs _ = []
53toPat :: Bool -> [Term] -> [Pat]
54toPat tc tms = evalState (mapM (\x -> toPat' x []) tms) []
55 where
56 toPat' (P (DCon t a) n _) args = do args' <- mapM (\x -> toPat' x []) args
57 return $ PCon n t args'
58 -- Typecase
59 toPat' (P (TCon t a) n _) args | tc
60 = do args' <- mapM (\x -> toPat' x []) args
61 return $ PCon n t args'
62 toPat' (Constant IType) [] | tc = return $ PCon (UN "Int") 1 []
63 toPat' (Constant FlType) [] | tc = return $ PCon (UN "Float") 2 []
64 toPat' (Constant ChType) [] | tc = return $ PCon (UN "Char") 3 []
65 toPat' (Constant StrType) [] | tc = return $ PCon (UN "String") 4 []
66 toPat' (Constant PtrType) [] | tc = return $ PCon (UN "Ptr") 5 []
67 toPat' (Constant BIType) [] | tc = return $ PCon (UN "Integer") 6 []
69 toPat' (P Bound n _) [] = do ns <- get
70 if n `elem` ns
71 then return PAny
72 else do put (n : ns)
73 return (PV n)
74 toPat' (App f a) args = toPat' f (a : args)
75 toPat' (Constant c) args
76 | isType c = return PAny
77 | otherwise = return $ PConst c
78 toPat' _ _ = return PAny
80 isType (I _) = False
81 isType (Fl _) = False
82 isType (Str _) = False
83 isType (Ch _) = False
84 isType _ = True
86data Partition = Cons [Clause]
87 | Vars [Clause]
89isVarPat (PV _ : ps , _) = True
90isVarPat (PAny : ps , _) = True
91isVarPat _ = False
93isConPat (PCon _ _ _ : ps, _) = True
94isConPat (PConst _ : ps, _) = True
95isConPat _ = False
97partition :: [Clause] -> [Partition]
98partition [] = []
99partition ms@(m : _)
100 | isVarPat m = let (vars, rest) = span isVarPat ms in
101 Vars vars : partition rest
102 | isConPat m = let (cons, rest) = span isConPat ms in
103 Cons cons : partition rest
104partition xs = error $ "Partition " ++ show xs
106match :: [Name] -> [Clause] -> SC -- error case
107 -> State CS SC
108match [] (([], ret) : _) err = return $ STerm ret -- run out of arguments
109match vs cs err = mixture vs (partition cs) err
111mixture :: [Name] -> [Partition] -> SC -> State CS SC
112mixture vs [] err = return err
113mixture vs (Cons ms : ps) err = do fallthrough <- mixture vs ps err
114 conRule vs ms fallthrough
115mixture vs (Vars ms : ps) err = do fallthrough <- mixture vs ps err
116 varRule vs ms fallthrough
118data ConType = CName Name Int -- named constructor
119 | CConst Const -- constant, not implemented yet
121data Group = ConGroup ConType -- Constructor
122 [([Pat], Clause)] -- arguments and rest of alternative
124conRule :: [Name] -> [Clause] -> SC -> State CS SC
125conRule (v:vs) cs err = do groups <- groupCons cs
126 caseGroups (v:vs) groups err
128caseGroups :: [Name] -> [Group] -> SC -> State CS SC
129caseGroups (v:vs) gs err = do g <- altGroups gs
130 return $ Case v g
131 where
132 altGroups [] = return [DefaultCase err]
133 altGroups (ConGroup (CName n i) args : cs)
134 = do g <- altGroup n i args
135 rest <- altGroups cs
136 return (g : rest)
137 altGroups (ConGroup (CConst c) args : cs)
138 = do g <- altConstGroup c args
139 rest <- altGroups cs
140 return (g : rest)
142 altGroup n i gs = do (newArgs, nextCs) <- argsToAlt gs
143 matchCs <- match (newArgs ++ vs) nextCs err
144 return $ ConCase n i newArgs matchCs
145 altConstGroup n gs = do (_, nextCs) <- argsToAlt gs
146 matchCs <- match vs nextCs err
147 return $ ConstCase n matchCs
149argsToAlt :: [([Pat], Clause)] -> State CS ([Name], [Clause])
150argsToAlt [] = return ([], [])
151argsToAlt rs@((r, m) : _)
152 = do newArgs <- getNewVars r
153 return (newArgs, addRs rs)
154 where
155 getNewVars [] = return []
156 getNewVars ((PV n) : ns) = do nsv <- getNewVars ns
157 return (n : nsv)
158 getNewVars (_ : ns) = do v <- getVar
159 nsv <- getNewVars ns
160 return (v : nsv)
161 addRs [] = []
162 addRs ((r, (ps, res)) : rs) = ((r++ps, res) : addRs rs)
164getVar :: State CS Name
165getVar = do v <- get; put (v+1); return (MN v "e")
167groupCons :: [Clause] -> State CS [Group]
168groupCons cs = gc [] cs
169 where
170 gc acc [] = return acc
171 gc acc ((p : ps, res) : cs) =
172 do acc' <- addGroup p ps res acc
173 gc acc' cs
174 addGroup p ps res acc = case p of
175 PCon con i args -> return $ addg con i args (ps, res) acc
176 PConst cval -> return $ addConG cval (ps, res) acc
177 pat -> fail $ show pat ++ " is not a constructor or constant (can't happen)"
179 addg con i conargs res [] = [ConGroup (CName con i) [(conargs, res)]]
180 addg con i conargs res (g@(ConGroup (CName n j) cs):gs)
181 | i == j = ConGroup (CName n i) (cs ++ [(conargs, res)]) : gs
182 | otherwise = g : addg con i conargs res gs
184 addConG con res [] = [ConGroup (CConst con) [([], res)]]
185 addConG con res (g@(ConGroup (CConst n) cs) : gs)
186 | con == n = ConGroup (CConst n) (cs ++ [([], res)]) : gs
187 | otherwise = g : addConG con res gs
189varRule :: [Name] -> [Clause] -> SC -> State CS SC
190varRule (v : vs) alts err =
191 do let alts' = map (repVar v) alts
192 match vs alts' err
193 where
194 repVar v (PV p : ps , res) = (ps, subst p (P Bound v undefined) res)
195 repVar v (PAny : ps , res) = (ps, res)
197{-
198mkOperator :: CaseDef -> [Value] -> Maybe Value
199mkOperator (CaseDef ns casetree) args
200 | length args /= length ns = Nothing
201 | otherwise = evalArgs (zip ns args) casetree
202 where
203 evalArgs map (Case n alts) =
204 do v <- lookup n map
205 (altmap, tm) <- findAlt (getValArgs v) alts map
206 evalArgs altmap tm
207 evalArgs map (STerm tm) =
208 evalArgs map (UnmatchedCase _) = Nothing
210 getValArgs tm = getValArgs' tm []
211 getValArgs' (VApp f a) as = getValArgs' f (a:as)
212 getValArgs' f as = (f, as)
214-}