a362c46b70
Nothing at all on hackage is using <&&> or <||>. (Also, <&&> should short-circuit on failure.)
100 lines
2.8 KiB
Haskell
100 lines
2.8 KiB
Haskell
{- A generic matcher.
|
|
-
|
|
- Can be used to check if a user-supplied condition,
|
|
- like "foo and ( bar or not baz )" matches. The condition must already
|
|
- be tokenized, and can contain arbitrary operations.
|
|
-
|
|
- If operations are not separated by and/or, they are defaulted to being
|
|
- anded together, so "foo bar baz" all must match.
|
|
-
|
|
- Is forgiving about misplaced closing parens, so "foo and (bar or baz"
|
|
- will be handled, as will "foo and ( bar or baz ) )"
|
|
-
|
|
- Copyright 2011 Joey Hess <joey@kitenet.net>
|
|
-
|
|
- Licensed under the GNU GPL version 3 or higher.
|
|
-}
|
|
|
|
module Utility.Matcher (
|
|
Token(..),
|
|
Matcher,
|
|
token,
|
|
generate,
|
|
match,
|
|
matchM,
|
|
matchesAny
|
|
) where
|
|
|
|
import Common
|
|
|
|
{- A Token can be an Operation of an arbitrary type, or one of a few
|
|
- predefined peices of syntax. -}
|
|
data Token op = Operation op | And | Or | Not | Open | Close
|
|
deriving (Show, Eq)
|
|
|
|
data Matcher op = MAny
|
|
| MAnd (Matcher op) (Matcher op)
|
|
| MOr (Matcher op) (Matcher op)
|
|
| MNot (Matcher op)
|
|
| MOp op
|
|
deriving (Show, Eq)
|
|
|
|
{- Converts a word of syntax into a token. Doesn't handle operations. -}
|
|
token :: String -> Token op
|
|
token "and" = And
|
|
token "or" = Or
|
|
token "not" = Not
|
|
token "(" = Open
|
|
token ")" = Close
|
|
token t = error $ "unknown token " ++ t
|
|
|
|
{- Converts a list of Tokens into a Matcher. -}
|
|
generate :: [Token op] -> Matcher op
|
|
generate = go MAny
|
|
where
|
|
go m [] = m
|
|
go m ts = uncurry go $ consume m ts
|
|
|
|
{- Consumes one or more Tokens, constructs a new Matcher,
|
|
- and returns unconsumed Tokens. -}
|
|
consume :: Matcher op -> [Token op] -> (Matcher op, [Token op])
|
|
consume m [] = (m, [])
|
|
consume m (t:ts) = go t
|
|
where
|
|
go And = cont $ m `MAnd` next
|
|
go Or = cont $ m `MOr` next
|
|
go Not = cont $ m `MAnd` MNot next
|
|
go Open = let (n, r) = consume next rest in (m `MAnd` n, r)
|
|
go Close = (m, ts)
|
|
go (Operation o) = (m `MAnd` MOp o, ts)
|
|
|
|
(next, rest) = consume MAny ts
|
|
cont v = (v, rest)
|
|
|
|
{- Checks if a Matcher matches, using a supplied function to check
|
|
- the value of Operations. -}
|
|
match :: (op -> v -> Bool) -> Matcher op -> v -> Bool
|
|
match a m v = go m
|
|
where
|
|
go MAny = True
|
|
go (MAnd m1 m2) = go m1 && go m2
|
|
go (MOr m1 m2) = go m1 || go m2
|
|
go (MNot m1) = not $ go m1
|
|
go (MOp o) = a o v
|
|
|
|
{- Runs a monadic Matcher, where Operations are actions in the monad. -}
|
|
matchM :: Monad m => Matcher (v -> m Bool) -> v -> m Bool
|
|
matchM m v = go m
|
|
where
|
|
go MAny = return True
|
|
go (MAnd m1 m2) = go m1 <&&> go m2
|
|
go (MOr m1 m2) = go m1 <||> go m2
|
|
go (MNot m1) = liftM not (go m1)
|
|
go (MOp o) = o v
|
|
|
|
{- Checks is a matcher contains no limits, and so (presumably) matches
|
|
- anything. Note that this only checks the trivial case; it is possible
|
|
- to construct matchers that match anything but are more complicated. -}
|
|
matchesAny :: Matcher a -> Bool
|
|
matchesAny MAny = True
|
|
matchesAny _ = False
|