blob: 9523e171655e378ce5522edb7b03fbcefa77983f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
{- monadic stuff
-
- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Utility.Monad where
import Data.Maybe
import Control.Monad (liftM)
{- Return the first value from a list, if any, satisfying the given
- predicate -}
firstM :: (Monad m) => (a -> m Bool) -> [a] -> m (Maybe a)
firstM _ [] = return Nothing
firstM p (x:xs) = do
q <- p x
if q
then return (Just x)
else firstM p xs
{- Returns true if any value in the list satisfies the preducate,
- stopping once one is found. -}
anyM :: (Monad m) => (a -> m Bool) -> [a] -> m Bool
anyM p = liftM isJust . firstM p
|
