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  1. data Maybe a

    copilot-language Copilot.Language.Prelude

    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.

  2. data Maybe a

    quaalude Essentials

    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.

  3. data Maybe a

    verset Verset

    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.

  4. data Maybe a

    xmonad-contrib XMonad.Config.Prime

    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.

  5. maybe :: b -> (a -> b) -> Maybe a -> b

    base Prelude

    The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is Nothing, the function returns the default value. Otherwise, it applies the function to the value inside the Just and returns the result.

    Examples

    Basic usage: 
    >>> maybe False odd (Just 3)
True

    >>> maybe False odd Nothing
False
    Read an integer from a string using readMaybe. If we succeed, return twice the integer; that is, apply (*2) to it. If instead we fail to parse an integer, return 0 by default: 
    >>> import GHC.Internal.Text.Read ( readMaybe )

>>> maybe 0 (*2) (readMaybe "5")
10

>>> maybe 0 (*2) (readMaybe "")
0
    Apply show to a Maybe Int. If we have Just n, we want to show the underlying Int n. But if we have Nothing, we return the empty string instead of (for example) "Nothing": 
    >>> maybe "" show (Just 5)
"5"

>>> maybe "" show Nothing
""

  6. maybe :: b -> (a -> b) -> Maybe a -> b

    base Data.Maybe

    The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is Nothing, the function returns the default value. Otherwise, it applies the function to the value inside the Just and returns the result.

    Examples

    Basic usage: 
    >>> maybe False odd (Just 3)
True

    >>> maybe False odd Nothing
False
    Read an integer from a string using readMaybe. If we succeed, return twice the integer; that is, apply (*2) to it. If instead we fail to parse an integer, return 0 by default: 
    >>> import GHC.Internal.Text.Read ( readMaybe )

>>> maybe 0 (*2) (readMaybe "5")
10

>>> maybe 0 (*2) (readMaybe "")
0
    Apply show to a Maybe Int. If we have Just n, we want to show the underlying Int n. But if we have Nothing, we return the empty string instead of (for example) "Nothing": 
    >>> maybe "" show (Just 5)
"5"

>>> maybe "" show Nothing
""

  7. maybe :: MonadGen m => m a -> m (Maybe a)

    hedgehog Hedgehog.Gen

    Generates a Nothing some of the time.

  8. maybe :: MonadGen m => m a -> m (Maybe a)

    hedgehog Hedgehog.Internal.Gen

    Generates a Nothing some of the time.

  9. maybe :: b -> (a -> b) -> Maybe a -> b

    hedgehog Hedgehog.Internal.Prelude

    The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is Nothing, the function returns the default value. Otherwise, it applies the function to the value inside the Just and returns the result.

    Examples

    Basic usage: 
    >>> maybe False odd (Just 3)
True

    >>> maybe False odd Nothing
False
    Read an integer from a string using readMaybe. If we succeed, return twice the integer; that is, apply (*2) to it. If instead we fail to parse an integer, return 0 by default: 
    >>> import GHC.Internal.Text.Read ( readMaybe )

>>> maybe 0 (*2) (readMaybe "5")
10

>>> maybe 0 (*2) (readMaybe "")
0
    Apply show to a Maybe Int. If we have Just n, we want to show the underlying Int n. But if we have Nothing, we return the empty string instead of (for example) "Nothing": 
    >>> maybe "" show (Just 5)
"5"

>>> maybe "" show Nothing
""

  10. maybe :: b -> (a -> b) -> Maybe a -> b

    ghc GHC.Prelude.Basic

    No documentation available.

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