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module GF.Command.TreeOperations (
treeOp,
allTreeOps,
treeChunks
) where
import PGF(PGF,CId,compute,unApp)
import PGF.Internal(Expr(..),unAppForm)
import Data.List
type TreeOp = [Expr] -> [Expr]
treeOp :: PGF -> String -> Maybe (Either TreeOp (CId -> TreeOp))
treeOp pgf f = fmap snd $ lookup f $ allTreeOps pgf
allTreeOps :: PGF -> [(String,(String,Either TreeOp (CId -> TreeOp)))]
allTreeOps pgf = [
("compute",("compute by using semantic definitions (def)",
Left $ map (compute pgf))),
("transfer",("syntactic transfer by applying function, recursively in subtrees",
Right $ \f -> map (transfer pgf f))),
("largest",("sort trees from largest to smallest, in number of nodes",
Left $ largest)),
("nub",("remove duplicate trees",
Left $ nub)),
("smallest",("sort trees from smallest to largest, in number of nodes",
Left $ smallest)),
("subtrees",("return all fully applied subtrees (stopping at abstractions), by default sorted from the largest",
Left $ concatMap subtrees)),
("funs",("return all fun functions appearing in the tree, with duplications",
Left $ concatMap funNodes))
]
largest :: [Expr] -> [Expr]
largest = reverse . smallest
smallest :: [Expr] -> [Expr]
smallest = sortBy (\t u -> compare (size t) (size u)) where
size t = case t of
EAbs _ _ e -> size e + 1
EApp e1 e2 -> size e1 + size e2 + 1
_ -> 1
treeChunks :: Expr -> [Expr]
treeChunks = snd . cks where
cks t = case unAppForm t of
(EFun f, ts) -> case unzip (map cks ts) of
(bs,_) | and bs -> (True, [t])
(_,cts) -> (False,concat cts)
(EMeta _, ts) -> (False,concatMap (snd . cks) ts)
_ -> (True, [t])
subtrees :: Expr -> [Expr]
subtrees t = t : case unApp t of
Just (f,ts) -> concatMap subtrees ts
_ -> [] -- don't go under abstractions
funNodes :: Expr -> [Expr]
funNodes t = case t of
EAbs _ _ e -> funNodes e
EApp e1 e2 -> funNodes e1 ++ funNodes e2
EFun _ -> [t]
_ -> [] -- not literals, metas, etc
--- simple-minded transfer; should use PGF.Expr.match
transfer :: PGF -> CId -> Expr -> Expr
transfer pgf f e = case transf e of
v | v /= appf e -> v
_ -> case e of
EApp g a -> EApp (transfer pgf f g) (transfer pgf f a)
_ -> e
where
appf = EApp (EFun f)
transf = compute pgf . appf
|
