| classes: | |
| documentation: |
----------------------------------------------------------------------------- --- This simple module defines the const functor known from Haskell's --- base libraries. It defines a wrapper around a constant value that --- "ignores" functions mapped over it. ----------------------------------------------------------------------------- |
| name: |
Data.Functor.Const |
| operations: | |
| sourcecode: |
module Data.Functor.Const
( Const (..)
) where
--- The `Const` functor which returns a constant for any `fmap`, i.e.,
--- a wrapper around a constant value that ignores functions mapped over it.
---
--- Example:
---
--- > fmap (++ "world") (Const "Hello")
--- Const "Hello"
newtype Const a _ = Const { getConst :: a }
deriving (Eq, Ord, Read, Show)
instance Functor (Const a) where
fmap _ (Const x) = Const x
|
| types: |
Const |
| unsafe: |
safe |