Hoogle Search

Within LTS Haskell 24.4 (ghc-9.10.2)

Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.

Exact lookup

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

   numeric-prelude	NumericPrelude.Base

   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

   numhask	NumHask.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
   ""
   

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

   basic-prelude	CorePrelude

   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
   ""
   

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

   classy-prelude	ClassyPrelude

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

   ghc-lib-parser	GHC.Data.Strict

   No documentation available.

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

   ghc-lib-parser	GHC.Prelude.Basic

   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 :: Decoder a -> Decoder (Maybe a)

   dhall	Dhall.Marshal.Decode

   Decode a Maybe.

   >>> input (maybe natural) "Some 1"
   Just 1
   

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

   foundation	Foundation

   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

   prelude-compat	Prelude2010

   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

    mixed-types-num	Numeric.MixedTypes.PreludeHiding

    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
    ""
    

Page 10 of many | Previous | Next