I propose to add the following utility function into Control.Applicative: cond :: (Alternative f) => (a -> Bool) -> a -> f a cond p a = if p a then pure a else empty Following is a typical use case: \x -> fromMaybe 0 $ cond (> 0) $ x - 10 which is the same as \x -> let y = x - 10 in if y > 0 then y else 0 Why the first one is better: 1. The control flow is evident and goes from right to left step by step. It’s not scattered around like in the second example. 2. No need to interrupt to imagine a name for a temporary variable. 3. Less noise. Now, since it’s generalised to Alternative one can imagine tons of other useful cases for this. Alternative titles: - conditional - partial Best regards, Nikita