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, namesUsed) where
4import Core.TT
6import Control.Monad.State
7import Data.List hiding (partition)
8import Debug.Trace
10data CaseDef = CaseDef [Name] SC [Term]
11 deriving Show
13data SC = Case Name [CaseAlt]
14 | STerm Term
15 | UnmatchedCase String -- error message
16 deriving Show
17{-!
18deriving instance Binary SC
19!-}
21data CaseAlt = ConCase Name Int [Name] SC
22 | ConstCase Const SC
23 | DefaultCase SC
24 deriving Show
25{-!
26deriving instance Binary CaseAlt
27!-}
29type CaseTree = SC
30type Clause = ([Pat], (Term, Term))
31type CS = ([Term], Int)
33-- simple terms can be inlined trivially - good for primitives in particular
34small :: SC -> Bool
35-- small (STerm t) = True
36small _ = False
38namesUsed :: SC -> [Name]
39namesUsed sc = nub $ nu' [] sc where
40 nu' ps (Case n alts) = concatMap (nua ps) alts
41 nu' ps (STerm t) = nut ps t
42 nu' ps _ = []
44 nua ps (ConCase n i args sc) = nu' (ps ++ args) sc
45 nua ps (ConstCase _ sc) = nu' ps sc
46 nua ps (DefaultCase sc) = nu' ps sc
48 nut ps (P _ n _) | n `elem` ps = []
49 | otherwise = [n]
50 nut ps (App f a) = nut ps f ++ nut ps a
51 nut ps (Bind n (Let t v) sc) = nut ps v ++ nut (n:ps) sc
52 nut ps (Bind n b sc) = nut (n:ps) sc
53 nut ps _ = []
55simpleCase :: Bool -> Bool -> [(Term, Term)] -> CaseDef
56simpleCase tc cover []
57 = CaseDef [] (UnmatchedCase "No pattern clauses") []
58simpleCase tc cover cs
59 = let pats = map (\ (l, r) -> (toPats tc l, (l, r))) cs
60 numargs = length (fst (head pats))
61 ns = take numargs args
62 (tree, st) = runState (match ns pats (defaultCase cover)) ([], numargs) in
63 CaseDef ns (prune tree) (fst st)
64 where args = map (\i -> MN i "e") [0..]
65 defaultCase True = STerm Erased
66 defaultCase False = UnmatchedCase "Error"
68data Pat = PCon Name Int [Pat]
69 | PConst Const
70 | PV Name
71 | PAny
72 deriving Show
74-- If there are repeated variables, take the *last* one (could be name shadowing
75-- in a where clause, so take the most recent).
77toPats :: Bool -> Term -> [Pat]
78toPats tc f = reverse (toPat tc (getArgs f)) where
79 getArgs (App f a) = a : getArgs f
80 getArgs _ = []
82toPat :: Bool -> [Term] -> [Pat]
83toPat tc tms = evalState (mapM (\x -> toPat' x []) tms) []
84 where
85 toPat' (P (DCon t a) n _) args = do args' <- mapM (\x -> toPat' x []) args
86 return $ PCon n t args'
87 -- Typecase
88 toPat' (P (TCon t a) n _) args | tc
89 = do args' <- mapM (\x -> toPat' x []) args
90 return $ PCon n t args'
91 toPat' (Constant IType) [] | tc = return $ PCon (UN "Int") 1 []
92 toPat' (Constant FlType) [] | tc = return $ PCon (UN "Float") 2 []
93 toPat' (Constant ChType) [] | tc = return $ PCon (UN "Char") 3 []
94 toPat' (Constant StrType) [] | tc = return $ PCon (UN "String") 4 []
95 toPat' (Constant PtrType) [] | tc = return $ PCon (UN "Ptr") 5 []
96 toPat' (Constant BIType) [] | tc = return $ PCon (UN "Integer") 6 []
98 toPat' (P Bound n _) [] = do ns <- get
99 if n `elem` ns
100 then return PAny
101 else do put (n : ns)
102 return (PV n)
103 toPat' (App f a) args = toPat' f (a : args)
104 toPat' (Constant (I c)) [] = return $ PConst (I c)
105 toPat' _ _ = return PAny
108data Partition = Cons [Clause]
109 | Vars [Clause]
111isVarPat (PV _ : ps , _) = True
112isVarPat (PAny : ps , _) = True
113isVarPat _ = False
115isConPat (PCon _ _ _ : ps, _) = True
116isConPat (PConst _ : ps, _) = True
117isConPat _ = False
119partition :: [Clause] -> [Partition]
120partition [] = []
121partition ms@(m : _)
122 | isVarPat m = let (vars, rest) = span isVarPat ms in
123 Vars vars : partition rest
124 | isConPat m = let (cons, rest) = span isConPat ms in
125 Cons cons : partition rest
126partition xs = error $ "Partition " ++ show xs
128match :: [Name] -> [Clause] -> SC -- error case
129 -> State CS SC
130match [] (([], ret) : xs) err
131 = do (ts, v) <- get
132 put (ts ++ (map (fst.snd) xs), v)
133 return $ STerm (snd ret) -- run out of arguments
134match vs cs err = do cs <- mixture vs (partition cs) err
135 return cs
137mixture :: [Name] -> [Partition] -> SC -> State CS SC
138mixture vs [] err = return err
139mixture vs (Cons ms : ps) err = do fallthrough <- mixture vs ps err
140 conRule vs ms fallthrough
141mixture vs (Vars ms : ps) err = do fallthrough <- mixture vs ps err
142 varRule vs ms fallthrough
144data ConType = CName Name Int -- named constructor
145 | CConst Const -- constant, not implemented yet
147data Group = ConGroup ConType -- Constructor
148 [([Pat], Clause)] -- arguments and rest of alternative
150conRule :: [Name] -> [Clause] -> SC -> State CS SC
151conRule (v:vs) cs err = do groups <- groupCons cs
152 caseGroups (v:vs) groups err
154caseGroups :: [Name] -> [Group] -> SC -> State CS SC
155caseGroups (v:vs) gs err = do g <- altGroups gs
156 return $ Case v g
157 where
158 altGroups [] = return [DefaultCase err]
159 altGroups (ConGroup (CName n i) args : cs)
160 = do g <- altGroup n i args
161 rest <- altGroups cs
162 return (g : rest)
163 altGroups (ConGroup (CConst c) args : cs)
164 = do g <- altConstGroup c args
165 rest <- altGroups cs
166 return (g : rest)
168 altGroup n i gs = do (newArgs, nextCs) <- argsToAlt gs
169 matchCs <- match (newArgs ++ vs) nextCs err
170 return $ ConCase n i newArgs matchCs
171 altConstGroup n gs = do (_, nextCs) <- argsToAlt gs
172 matchCs <- match vs nextCs err
173 return $ ConstCase n matchCs
175argsToAlt :: [([Pat], Clause)] -> State CS ([Name], [Clause])
176argsToAlt [] = return ([], [])
177argsToAlt rs@((r, m) : _)
178 = do newArgs <- getNewVars r
179 return (newArgs, addRs rs)
180 where
181 getNewVars [] = return []
182 getNewVars ((PV n) : ns) = do nsv <- getNewVars ns
183 return (n : nsv)
184 getNewVars (_ : ns) = do v <- getVar
185 nsv <- getNewVars ns
186 return (v : nsv)
187 addRs [] = []
188 addRs ((r, (ps, res)) : rs) = ((r++ps, res) : addRs rs)
190getVar :: State CS Name
191getVar = do (t, v) <- get; put (t, v+1); return (MN v "e")
193groupCons :: [Clause] -> State CS [Group]
194groupCons cs = gc [] cs
195 where
196 gc acc [] = return acc
197 gc acc ((p : ps, res) : cs) =
198 do acc' <- addGroup p ps res acc
199 gc acc' cs
200 addGroup p ps res acc = case p of
201 PCon con i args -> return $ addg con i args (ps, res) acc
202 PConst cval -> return $ addConG cval (ps, res) acc
203 pat -> fail $ show pat ++ " is not a constructor or constant (can't happen)"
205 addg con i conargs res [] = [ConGroup (CName con i) [(conargs, res)]]
206 addg con i conargs res (g@(ConGroup (CName n j) cs):gs)
207 | i == j = ConGroup (CName n i) (cs ++ [(conargs, res)]) : gs
208 | otherwise = g : addg con i conargs res gs
210 addConG con res [] = [ConGroup (CConst con) [([], res)]]
211 addConG con res (g@(ConGroup (CConst n) cs) : gs)
212 | con == n = ConGroup (CConst n) (cs ++ [([], res)]) : gs
213 | otherwise = g : addConG con res gs
215varRule :: [Name] -> [Clause] -> SC -> State CS SC
216varRule (v : vs) alts err =
217 do let alts' = map (repVar v) alts
218 match vs alts' err
219 where
220 repVar v (PV p : ps , (lhs, res)) = (ps, (lhs, subst p (P Bound v (V 0)) res))
221 repVar v (PAny : ps , res) = (ps, res)
223prune :: SC -> SC
224prune (Case n alts)
225 = let alts' = map pruneAlt $
226 filter notErased alts in
227 case alts' of
228 [] -> STerm Erased
229 as -> Case n as
230 where pruneAlt (ConCase n i ns sc) = ConCase n i ns (prune sc)
231 pruneAlt (ConstCase c sc) = ConstCase c (prune sc)
232 pruneAlt (DefaultCase sc) = DefaultCase (prune sc)
234 notErased (DefaultCase (STerm Erased)) = False
235 notErased _ = True
236prune t = t