gistfile1.hs

-- A simple definition without using any fancy functions.
haskell>let ifMaybe pred value = if pred value then Just value else Nothing
haskell>:t ifMaybe
ifMaybe :: (a -> Bool) -> a -> Maybe a
haskell>ifMaybe (const True) 2
Just 2
haskell>ifMaybe (const False) 2
Nothing

-- Using functions from standard library.
haskell>let ifMaybe pred value = mfilter pred $ Just value
haskell>:t ifMaybe
ifMaybe :: (a -> Bool) -> a -> Maybe a
haskell>ifMaybe (const True) 2
Just 2
haskell>ifMaybe (const False) 2
Nothing

-- A point-free version that uses section of (.).
haskell>let ifMaybe = (. Just) . mfilter
haskell>:t ifMaybe
ifMaybe :: (a -> Bool) -> a -> Maybe a
haskell>ifMaybe (const True) 2
Just 2
haskell>ifMaybe (const False) 2
Nothing

-- Same thing written with (<.|) combinator.
haskell>let ifMaybe = mfilter <.| Just
haskell>:t ifMaybe
ifMaybe :: (a -> Bool) -> a -> Maybe a
haskell>ifMaybe (const True) 2
Just 2
haskell>ifMaybe (const False) 2
Nothing
haskell>

With some help of @djinn and @pl commands of lambdabot...

Prelude Control.Arrow Control.Applicative> let regular = (. (,)) . (.)
Prelude Control.Arrow Control.Applicative> :t regular
regular :: ((a, b) -> c) -> a -> b -> c
Prelude Control.Arrow Control.Applicative> let f |.> g = regular $ f . uncurry g
Prelude Control.Arrow Control.Applicative> :t (|.>)
(|.>) :: (b1 -> c) -> (a -> b -> b1) -> a -> b -> c