Safe Haskell | None |
---|---|

Language | Haskell98 |

A strict version of the `Maybe`

type.

Import qualified, as in
```
import qualified Agda.Utils.Maybe.Strict as Strict
```

Copyright : (c) 2006-2007 Roman Leshchinskiy (c) 2013 Simon Meier License : BSD-style (see the file LICENSE)

Copyright : (c) 2014 Andreas Abel

- toStrict :: Maybe a -> Maybe a
- toLazy :: Maybe a -> Maybe a
- listToMaybe :: [a] -> Maybe a
- maybeToList :: Maybe a -> [a]
- catMaybes :: [Maybe a] -> [a]
- mapMaybe :: (a -> Maybe b) -> [a] -> [b]
- unionMaybeWith :: (a -> a -> a) -> Maybe a -> Maybe a -> Maybe a
- unzipMaybe :: Maybe (a, b) -> (Maybe a, Maybe b)
- filterMaybe :: (a -> Bool) -> a -> Maybe a
- forMaybe :: [a] -> (a -> Maybe b) -> [b]
- caseMaybe :: Maybe a -> b -> (a -> b) -> b
- maybeM :: Monad m => m b -> (a -> m b) -> m (Maybe a) -> m b
- fromMaybeM :: Monad m => m a -> m (Maybe a) -> m a
- caseMaybeM :: Monad m => m (Maybe a) -> m b -> (a -> m b) -> m b
- ifJustM :: Monad m => m (Maybe a) -> (a -> m b) -> m b -> m b
- whenJust :: Monad m => Maybe a -> (a -> m ()) -> m ()
- whenJustM :: Monad m => m (Maybe a) -> (a -> m ()) -> m ()

# Documentation

listToMaybe :: [a] -> Maybe a Source

Analogous to `listToMaybe`

in Data.Maybe.

maybeToList :: Maybe a -> [a] Source

Analogous to `maybeToList`

in Data.Maybe.

catMaybes :: [Maybe a] -> [a] Source

Analogous to `catMaybes`

in Data.Maybe.

mapMaybe :: (a -> Maybe b) -> [a] -> [b] Source

Analogous to `mapMaybe`

in Data.Maybe.

# Collection operations.

unionMaybeWith :: (a -> a -> a) -> Maybe a -> Maybe a -> Maybe a Source

`unionWith`

for collections of size <= 1.

unzipMaybe :: Maybe (a, b) -> (Maybe a, Maybe b) Source

Unzipping a list of length <= 1.

filterMaybe :: (a -> Bool) -> a -> Maybe a Source

Filtering a singleton list.

filterMaybe p a =`listToMaybe`

(`filter`

p [a])

# Conditionals and loops.

forMaybe :: [a] -> (a -> Maybe b) -> [b] Source

Version of `mapMaybe`

with different argument ordering.

caseMaybe :: Maybe a -> b -> (a -> b) -> b Source

Version of `maybe`

with different argument ordering.
Often, we want to case on a `Maybe`

, do something interesting
in the `Just`

case, but only a default action in the `Nothing`

case. Then, the argument ordering of `caseMaybe`

is preferable.

caseMaybe m err f = flip (maybe err) m f

# Monads and Maybe.

fromMaybeM :: Monad m => m a -> m (Maybe a) -> m a Source

Monadic version of `fromMaybe`

.

caseMaybeM :: Monad m => m (Maybe a) -> m b -> (a -> m b) -> m b Source

ifJustM :: Monad m => m (Maybe a) -> (a -> m b) -> m b -> m b Source

`caseMaybeM`

with flipped branches.

whenJustM :: Monad m => m (Maybe a) -> (a -> m ()) -> m () Source

`caseMaybeM`

without the `Nothing`

case.