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Within LTS Haskell 24.3 (ghc-9.10.2)

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1. 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
   ""
   

2. 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
   ""
   

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

   hedgehog	Hedgehog.Gen

   Generates a Nothing some of the time.

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

   hedgehog	Hedgehog.Internal.Gen

   Generates a Nothing some of the time.

5. 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
   ""
   

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

   ghc	GHC.Prelude.Basic

   No documentation available.

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

   strict	Data.Strict.Maybe

   Given a default value, a function and a Maybe value, yields the default value if the Maybe value is Nothing and applies the function to the value stored in the Just otherwise.

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

   rio	RIO.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 :: b -> (a -> b) -> Maybe a -> b

   errors	Control.Error

   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

    Cabal-syntax	Distribution.Compat.Prelude

    No documentation available.

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