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Within LTS Haskell 24.4 (ghc-9.10.2)

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  1. maybe :: forall (m :: Type -> Type) a b . Monad m => (a -> Maybe b) -> Fold m a (Maybe b)

    streamly-core Streamly.Internal.Data.Fold

    Consume a single input and transform it using the supplied Maybe returning function. Pre-release

  2. maybe :: forall (m :: Type -> Type) a b . Monad m => (a -> Maybe b) -> Parser a m b

    streamly-core Streamly.Internal.Data.Parser

    Map a Maybe returning function on the next element in the stream. The parser fails if the function returns Nothing otherwise returns the Just value. 

    >>> toEither = Maybe.maybe (Left "maybe: predicate failed") Right

>>> maybe f = Parser.either (toEither . f)

    >>> maybe f = Parser.fromFoldMaybe "maybe: predicate failed" (Fold.maybe f)
    Pre-release

  3. maybe :: Decoder a -> Decoder (Maybe a)

    aeson-combinators Data.Aeson.Combinators.Decode

    Try a decoder and get back a 'Just a' if it succeeds and Nothing if it fails. In other words, this decoder always succeeds with a 'Maybe a' value. 

    >>> decode (maybe string) "42"
Just Nothing

>>> decode (maybe int) "42"
Just (Just 42)

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

    clash-prelude Clash.HaskellPrelude

    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
""

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

    data-memocombinators Data.MemoCombinators

    No documentation available.

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

    dimensional Numeric.Units.Dimensional.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
""

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

    distribution-opensuse OpenSuse.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
""

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

    faktory Faktory.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
""

  9. maybe :: (AbsRel ar, FileDir fd) => String -> Maybe (Path ar fd)

    pathtype System.Path

    No documentation available.

  10. maybe :: (System os, AbsRel ar, FileDir fd) => String -> Maybe (Path os ar fd)

    pathtype System.Path.Generic

    This function is intended for checking and parsing paths provided as user input. 

    fmap Posix.toString (Posix.maybePath "/" :: Maybe Posix.AbsDir) == Just "/"

    fmap Posix.toString (Posix.maybePath "/" :: Maybe Posix.AbsFile) == Nothing

    fmap Posix.toString (Posix.maybePath "/" :: Maybe Posix.RelDir) == Nothing

    fmap Posix.toString (Posix.maybePath "/" :: Maybe Posix.RelFile) == Nothing

    fmap Posix.toString (Posix.maybePath "/tmp" :: Maybe Posix.AbsDir) == Just "/tmp"

    fmap Posix.toString (Posix.maybePath "/tmp" :: Maybe Posix.AbsFile) == Just "/tmp"

    fmap Posix.toString (Posix.maybePath "/tmp" :: Maybe Posix.RelDir) == Nothing

    fmap Posix.toString (Posix.maybePath "/tmp" :: Maybe Posix.RelFile) == Nothing

    fmap Posix.toString (Posix.maybePath "/tmp/" :: Maybe Posix.AbsDir) == Just "/tmp"

    fmap Posix.toString (Posix.maybePath "/tmp/" :: Maybe Posix.AbsFile) == Nothing

    fmap Posix.toString (Posix.maybePath "/tmp/" :: Maybe Posix.RelDir) == Nothing

    fmap Posix.toString (Posix.maybePath "/tmp/" :: Maybe Posix.RelFile) == Nothing

    fmap Posix.toString (Posix.maybePath "/tmp" :: Maybe Posix.AbsRelFileDir) == Just "/tmp"

    fmap Posix.toString (Posix.maybePath "/tmp/" :: Maybe Posix.AbsRelFileDir) == Just "/tmp"

    fmap Posix.toString (Posix.maybePath "file.txt" :: Maybe Posix.RelFile) == Just "file.txt"

    fmap Posix.toString (Posix.maybePath "file.txt" :: Maybe Posix.AbsFile) == Nothing

    fmap Windows.toString (Windows.maybePath "\\tmp" :: Maybe Windows.AbsDir) == Just "\\tmp"

    fmap Windows.toString (Windows.maybePath "a:\\tmp" :: Maybe Windows.AbsDir) == Just "a:\\tmp"

    fmap Windows.toString (Windows.maybePath "a:tmp" :: Maybe Windows.AbsDir) == Just "a:tmp"

    fmap Windows.toString (Windows.maybePath "a:\\" :: Maybe Windows.AbsDir) == Just "a:\\"

    fmap Windows.toString (Windows.maybePath "a:" :: Maybe Windows.AbsDir) == Just "a:"

    fmap Windows.toString (Windows.maybePath "tmp" :: Maybe Windows.RelDir) == Just "tmp"

    fmap Windows.toString (Windows.maybePath "\\tmp" :: Maybe Windows.RelDir) == Nothing

    fmap Windows.toString (Windows.maybePath "a:\\tmp" :: Maybe Windows.RelDir) == Nothing

    fmap Windows.toString (Windows.maybePath "a:tmp" :: Maybe Windows.RelDir) == Nothing

    fmap Windows.toString (Windows.maybePath "tmp" :: Maybe Windows.AbsDir) == Nothing

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