 | utility-ht-0.0.5.1: Various small helper functions for Lists, Maybes, Tuples, Functions | Source code | Contents | Index |
| Data.Maybe.HT |
| toMaybe :: Bool -> a -> Maybe a |
| (?->) :: Maybe a -> (a -> b) -> Maybe b |
| alternatives :: a -> [Maybe a] -> a |
| toMaybe :: Bool -> a -> Maybe a | Source |
| (?->) :: Maybe a -> (a -> b) -> Maybe b | Source |
This is an infix version of fmap for writing Data.Bool.HT.select style expressions using test functions, that produce Maybes.
The precedence is chosen to be higher than '(:)', in order to allow:
alternatives default $
checkForA ?-> (\a -> f a) :
checkForB ?-> (\b -> g b) :
[]
The operation is left associative in order to allow to write
checkForA ?-> f ?-> g
which is equivalent to
checkForA ?-> g . f
due to the functor law.
| alternatives :: a -> [Maybe a] -> a | Source |