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
16{-!
17deriving instance Binary SC
18!-}
20data CaseAlt = ConCase Name Int [Name] SC
21 | ConstCase Const SC
22 | DefaultCase SC
23 deriving Show
24{-!
25deriving instance Binary CaseAlt
26!-}
28type CaseTree = SC
29type Clause = ([Pat], Term)
30type CS = Int
32-- simple terms can be inlined trivially - good for primitives in particular
33small :: SC -> Bool
34-- small (STerm t) = True
35small _ = False
37simpleCase :: Bool -> Bool -> [(Term, Term)] -> CaseDef
38simpleCase tc cover []
39 = CaseDef [] (UnmatchedCase "No pattern clauses")
40simpleCase tc cover cs
41 = let pats = map (\ (l, r) -> (toPats tc l, r)) cs
42 numargs = length (fst (head pats))
43 ns = take numargs args
44 tree = evalState (match ns pats (defaultCase cover)) numargs in
45 CaseDef ns (prune tree)
46 where args = map (\i -> MN i "e") [0..]
47 defaultCase True = STerm Erased
48 defaultCase False = UnmatchedCase "Error"
50data Pat = PCon Name Int [Pat]
51 | PConst Const
52 | PV Name
53 | PAny
54 deriving Show
56-- If there are repeated variables, take the *last* one (could be name shadowing
57-- in a where clause, so take the most recent).
59toPats :: Bool -> Term -> [Pat]
60toPats tc f = reverse (toPat tc (getArgs f)) where
61 getArgs (App f a) = a : getArgs f
62 getArgs _ = []
64toPat :: Bool -> [Term] -> [Pat]
65toPat tc tms = evalState (mapM (\x -> toPat' x []) tms) []
66 where
67 toPat' (P (DCon t a) n _) args = do args' <- mapM (\x -> toPat' x []) args
68 return $ PCon n t args'
69 -- Typecase
70 toPat' (P (TCon t a) n _) args | tc
71 = do args' <- mapM (\x -> toPat' x []) args
72 return $ PCon n t args'
73 toPat' (Constant IType) [] | tc = return $ PCon (UN "Int") 1 []
74 toPat' (Constant FlType) [] | tc = return $ PCon (UN "Float") 2 []
75 toPat' (Constant ChType) [] | tc = return $ PCon (UN "Char") 3 []
76 toPat' (Constant StrType) [] | tc = return $ PCon (UN "String") 4 []
77 toPat' (Constant PtrType) [] | tc = return $ PCon (UN "Ptr") 5 []
78 toPat' (Constant BIType) [] | tc = return $ PCon (UN "Integer") 6 []
80 toPat' (P Bound n _) [] = do ns <- get
81 if n `elem` ns
82 then return PAny
83 else do put (n : ns)
84 return (PV n)
85 toPat' (App f a) args = toPat' f (a : args)
86 toPat' (Constant (I c)) [] = return $ PConst (I c)
87 toPat' _ _ = return PAny
90data Partition = Cons [Clause]
91 | Vars [Clause]
93isVarPat (PV _ : ps , _) = True
94isVarPat (PAny : ps , _) = True
95isVarPat _ = False
97isConPat (PCon _ _ _ : ps, _) = True
98isConPat (PConst _ : ps, _) = True
99isConPat _ = False
101partition :: [Clause] -> [Partition]
102partition [] = []
103partition ms@(m : _)
104 | isVarPat m = let (vars, rest) = span isVarPat ms in
105 Vars vars : partition rest
106 | isConPat m = let (cons, rest) = span isConPat ms in
107 Cons cons : partition rest
108partition xs = error $ "Partition " ++ show xs
110match :: [Name] -> [Clause] -> SC -- error case
111 -> State CS SC
112match [] (([], ret) : _) err = return $ STerm ret -- run out of arguments
113match vs cs err = mixture vs (partition cs) err
115mixture :: [Name] -> [Partition] -> SC -> State CS SC
116mixture vs [] err = return err
117mixture vs (Cons ms : ps) err = do fallthrough <- mixture vs ps err
118 conRule vs ms fallthrough
119mixture vs (Vars ms : ps) err = do fallthrough <- mixture vs ps err
120 varRule vs ms fallthrough
122data ConType = CName Name Int -- named constructor
123 | CConst Const -- constant, not implemented yet
125data Group = ConGroup ConType -- Constructor
126 [([Pat], Clause)] -- arguments and rest of alternative
128conRule :: [Name] -> [Clause] -> SC -> State CS SC
129conRule (v:vs) cs err = do groups <- groupCons cs
130 caseGroups (v:vs) groups err
132caseGroups :: [Name] -> [Group] -> SC -> State CS SC
133caseGroups (v:vs) gs err = do g <- altGroups gs
134 return $ Case v g
135 where
136 altGroups [] = return [DefaultCase err]
137 altGroups (ConGroup (CName n i) args : cs)
138 = do g <- altGroup n i args
139 rest <- altGroups cs
140 return (g : rest)
141 altGroups (ConGroup (CConst c) args : cs)
142 = do g <- altConstGroup c args
143 rest <- altGroups cs
144 return (g : rest)
146 altGroup n i gs = do (newArgs, nextCs) <- argsToAlt gs
147 matchCs <- match (newArgs ++ vs) nextCs err
148 return $ ConCase n i newArgs matchCs
149 altConstGroup n gs = do (_, nextCs) <- argsToAlt gs
150 matchCs <- match vs nextCs err
151 return $ ConstCase n matchCs
153argsToAlt :: [([Pat], Clause)] -> State CS ([Name], [Clause])
154argsToAlt [] = return ([], [])
155argsToAlt rs@((r, m) : _)
156 = do newArgs <- getNewVars r
157 return (newArgs, addRs rs)
158 where
159 getNewVars [] = return []
160 getNewVars ((PV n) : ns) = do nsv <- getNewVars ns
161 return (n : nsv)
162 getNewVars (_ : ns) = do v <- getVar
163 nsv <- getNewVars ns
164 return (v : nsv)
165 addRs [] = []
166 addRs ((r, (ps, res)) : rs) = ((r++ps, res) : addRs rs)
168getVar :: State CS Name
169getVar = do v <- get; put (v+1); return (MN v "e")
171groupCons :: [Clause] -> State CS [Group]
172groupCons cs = gc [] cs
173 where
174 gc acc [] = return acc
175 gc acc ((p : ps, res) : cs) =
176 do acc' <- addGroup p ps res acc
177 gc acc' cs
178 addGroup p ps res acc = case p of
179 PCon con i args -> return $ addg con i args (ps, res) acc
180 PConst cval -> return $ addConG cval (ps, res) acc
181 pat -> fail $ show pat ++ " is not a constructor or constant (can't happen)"
183 addg con i conargs res [] = [ConGroup (CName con i) [(conargs, res)]]
184 addg con i conargs res (g@(ConGroup (CName n j) cs):gs)
185 | i == j = ConGroup (CName n i) (cs ++ [(conargs, res)]) : gs
186 | otherwise = g : addg con i conargs res gs
188 addConG con res [] = [ConGroup (CConst con) [([], res)]]
189 addConG con res (g@(ConGroup (CConst n) cs) : gs)
190 | con == n = ConGroup (CConst n) (cs ++ [([], res)]) : gs
191 | otherwise = g : addConG con res gs
193varRule :: [Name] -> [Clause] -> SC -> State CS SC
194varRule (v : vs) alts err =
195 do let alts' = map (repVar v) alts
196 match vs alts' err
197 where
198 repVar v (PV p : ps , res) = (ps, subst p (P Bound v (V 0)) res)
199 repVar v (PAny : ps , res) = (ps, res)
201prune :: SC -> SC
202prune (Case n alts)
203 = let alts' = map pruneAlt $
204 filter notErased alts in
205 case alts' of
206 [] -> STerm Erased
207 as -> Case n as
208 where pruneAlt (ConCase n i ns sc) = ConCase n i ns (prune sc)
209 pruneAlt (ConstCase c sc) = ConstCase c (prune sc)
210 pruneAlt (DefaultCase sc) = DefaultCase (prune sc)
212 notErased (DefaultCase (STerm Erased)) = False
213 notErased _ = True
214prune t = t