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Tidied up a use of impredicative types

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This commit is contained in:
Neil Brown 2010-04-10 19:40:54 +00:00
parent f12f0f9219
commit fe1ef8f6f5
1 changed files with 6 additions and 7 deletions
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13
common/TreeUtils.hs
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@ -352,14 +352,14 @@ checkTreeForConstr :: Data a => [Constr] -> a -> [AnyDataItem]
checkTreeForConstr cons = makeCheckFunction $ zip (map constrType cons) cons
where
makeCheckFunction :: Data a => [(DataType, Constr)] -> (a -> [AnyDataItem])
makeCheckFunction tcs = listify' (anyFunc $ ((map makeCheckFunction' tcs) :: [GenericQ Bool]))
makeCheckFunction tcs = listify' (anyFunc $ ((map makeCheckFunction' tcs) :: [GenericQ' Bool]))
-- anyFunc takes a list of generic queries, and returns a single generic query that ORs the results together
-- Note that this is not the same as using foldl and extQ, because extQ deals with type-specific cases,
-- not generic queries as we have here.
anyFunc :: [GenericQ Bool] -> GenericQ Bool
anyFunc :: [GenericQ' Bool] -> GenericQ Bool
anyFunc [] _ = False
anyFunc (f:fs) x = (f x) || (anyFunc fs x)
anyFunc (f:fs) x = (unGQ f x) || (anyFunc fs x)
-- listify expects a type-specific function as its parameter, not a generic query.
-- This function only differs from listify by using a generic query, and wrapping the result in an AnyDataItem wrapper.
@ -370,10 +370,9 @@ checkTreeForConstr cons = makeCheckFunction $ zip (map constrType cons) cons
f' x = if (f x) then [ADI x] else []
-- checks that the DataType and Constr match the given Data item.
makeCheckFunction' :: (DataType, Constr) -> (GenericQ Bool)
makeCheckFunction' (tr,con) d = (show (dataTypeOf d) == show tr) && (c == con) && (show c == show con)
where
c = toConstr d
makeCheckFunction' :: (DataType, Constr) -> (GenericQ' Bool)
makeCheckFunction' (tr,con) = GQ (\d -> let c = toConstr d
in (show (dataTypeOf d) == show tr) && (c == con) && (show c == show con))
-- | Converts a 0-argument constructor into its Constr form.
con0 :: Data a => a -> Constr