8a3edfd2e2
This file should have been in the earlier patch at 22:01 on Mon Aug 20, but it got missed out by accident.
35 lines
1.1 KiB
Haskell
35 lines
1.1 KiB
Haskell
module Pattern (Pattern(..)) where
|
|
|
|
import Data.Generics
|
|
|
|
data Pattern =
|
|
-- | We don't care what the value is -- will match against any item
|
|
DontCare
|
|
-- | A named "item of interest". Given the specified key, all data items with the same key should be identical (otherwise match errors will be given)
|
|
| Named String Pattern
|
|
-- | A constructed item. This is special because the sub-items may not be of the right type for the constructor,
|
|
-- because they may be special items (such as DontCare)
|
|
| Match Constr [Pattern]
|
|
deriving (Typeable,Show,Eq)
|
|
|
|
--No proper gunfold, as I still can't figure out to implement it (Constr is problematic)
|
|
instance Data Pattern where
|
|
toConstr (DontCare) = constr_DontCare
|
|
toConstr (Named {}) = constr_Named
|
|
toConstr (Match {}) = constr_Match
|
|
|
|
gunfold _ _ _ = error "gunfold Pattern"
|
|
|
|
dataTypeOf _ = ty_Pattern
|
|
|
|
ty_Pattern = mkDataType "TreeUtil.Pattern"
|
|
[
|
|
constr_DontCare
|
|
,constr_Named
|
|
,constr_Match
|
|
]
|
|
|
|
constr_DontCare = mkConstr ty_Pattern "DontCare" [] Prefix
|
|
constr_Named = mkConstr ty_Pattern "Named" [] Prefix
|
|
constr_Match = mkConstr ty_Pattern "Match" [] Prefix
|