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| author | Julie Moronuki <jdog74@gmail.com> | 2017-10-31 23:28:46 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2017-11-06 16:43:35 -0500 |
| commit | 275ac8ef0a0081f16abbfb8934e10cf271573768 (patch) | |
| tree | 1dbc921b1e8584beb8a5b118a9202564b30aef9f | |
| parent | 66b5b3eef1aa9fa9f192a85847d34b2756bec33f (diff) | |
| download | haskell-275ac8ef0a0081f16abbfb8934e10cf271573768.tar.gz | |
base: Add examples to Bifunctor documentation
| -rw-r--r-- | libraries/base/Data/Bifunctor.hs | 37 |
1 files changed, 36 insertions, 1 deletions
diff --git a/libraries/base/Data/Bifunctor.hs b/libraries/base/Data/Bifunctor.hs index 5441605ecf..04de5ad7f2 100644 --- a/libraries/base/Data/Bifunctor.hs +++ b/libraries/base/Data/Bifunctor.hs @@ -20,7 +20,15 @@ module Data.Bifunctor import Control.Applicative ( Const(..) ) import GHC.Generics ( K1(..) ) --- | Formally, the class 'Bifunctor' represents a bifunctor +-- | A bifunctor is a type constructor that takes +-- two type arguments and is a functor in /both/ arguments. That +-- is, unlike with 'Functor', a type constructor such as 'Either' +-- does not need to be partially applied for a 'Bifunctor' +-- instance, and the methods in this class permit mapping +-- functions over the 'Left' value or the 'Right' value, +-- or both at the same time. +-- +-- Formally, the class 'Bifunctor' represents a bifunctor -- from @Hask@ -> @Hask@. -- -- Intuitively it is a bifunctor where both the first and second @@ -59,22 +67,49 @@ class Bifunctor p where -- | Map over both arguments at the same time. -- -- @'bimap' f g ≡ 'first' f '.' 'second' g@ + -- + -- ==== __Examples__ + -- >>> bimap toUpper (+1) ('j', 3) + -- ('J',4) + -- + -- >>> bimap toUpper (+1) (Left 'j') + -- Left 'J' + -- + -- >>> bimap toUpper (+1) (Right 3) + -- Right 4 bimap :: (a -> b) -> (c -> d) -> p a c -> p b d bimap f g = first f . second g + -- | Map covariantly over the first argument. -- -- @'first' f ≡ 'bimap' f 'id'@ + -- + -- ==== __Examples__ + -- >>> first toUpper ('j', 3) + -- ('J',3) + -- + -- >>> first toUpper (Left 'j') + -- Left 'J' first :: (a -> b) -> p a c -> p b c first f = bimap f id + -- | Map covariantly over the second argument. -- -- @'second' ≡ 'bimap' 'id'@ + -- + -- ==== __Examples__ + -- >>> second (+1) ('j', 3) + -- ('j',4) + -- + -- >>> second (+1) (Right 3) + -- Right 4 second :: (b -> c) -> p a b -> p a c second = bimap id + -- | @since 4.8.0.0 instance Bifunctor (,) where bimap f g ~(a, b) = (f a, g b) |