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| Data.Maybe | | Portability | portable | | Stability | experimental | | Maintainer | libraries@haskell.org |
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| Description |
| The Maybe type, and associated operations.
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| Synopsis |
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| Documentation |
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| data Maybe a |
The Maybe type encapsulates an optional value. A value of type
Maybe a either contains a value of type a (represented as Just a),
or it is empty (represented as Nothing). Using Maybe is a good way to
deal with errors or exceptional cases without resorting to drastic
measures such as error. The Maybe type is also a monad. It is a simple kind of error
monad, where all errors are represented by Nothing. A richer
error monad can be built using the Either type. | | Constructors | | | Instances | |
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| maybe :: b -> (a -> b) -> Maybe a -> b |
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| isJust :: Maybe a -> Bool |
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| isNothing :: Maybe a -> Bool |
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| fromJust :: Maybe a -> a |
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| fromMaybe :: a -> Maybe a -> a |
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| listToMaybe :: [a] -> Maybe a |
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| maybeToList :: Maybe a -> [a] |
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| catMaybes :: [Maybe a] -> [a] |
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| mapMaybe :: (a -> Maybe b) -> [a] -> [b] |
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| Produced by Haddock version 0.4 |
