mirror of
https://github.com/sharkdp/bat
synced 2024-11-24 12:53:22 +00:00
89 lines
2.6 KiB
Text
Vendored
89 lines
2.6 KiB
Text
Vendored
-- | This module defines a datatype `Pair` together with a few useful instances
|
|
-- | and helper functions. Note that this is not just `Tuple a a` but rather a
|
|
-- | list with exactly two elements. Specifically, the `Functor` instance maps
|
|
-- | over both values (in contrast to the `Functor` instance for `Tuple a`).
|
|
module Data.Pair
|
|
( Pair(..)
|
|
, (~)
|
|
, fst
|
|
, snd
|
|
, curry
|
|
, uncurry
|
|
, swap
|
|
) where
|
|
|
|
import Prelude
|
|
|
|
import Data.Foldable (class Foldable)
|
|
import Data.Traversable (class Traversable)
|
|
import Data.Distributive (class Distributive)
|
|
|
|
import Test.QuickCheck.Arbitrary (class Arbitrary, arbitrary)
|
|
|
|
-- | A pair simply consists of two values of the same type.
|
|
data Pair a = Pair a a
|
|
|
|
infixl 6 Pair as ~
|
|
|
|
-- | Returns the first component of a pair.
|
|
fst ∷ ∀ a. Pair a → a
|
|
fst (x ~ _) = x
|
|
|
|
-- | Returns the second component of a pair.
|
|
snd ∷ ∀ a. Pair a → a
|
|
snd (_ ~ y) = y
|
|
|
|
-- | Turn a function that expects a pair into a function of two arguments.
|
|
curry ∷ ∀ a b. (Pair a → b) → a → a → b
|
|
curry f x y = f (x ~ y)
|
|
|
|
-- | Turn a function of two arguments into a function that expects a pair.
|
|
uncurry ∷ ∀ a b. (a → a → b) → Pair a → b
|
|
uncurry f (x ~ y) = f x y
|
|
|
|
-- | Exchange the two components of the pair
|
|
swap ∷ ∀ a. Pair a → Pair a
|
|
swap (x ~ y) = y ~ x
|
|
|
|
derive instance eqPair ∷ Eq a ⇒ Eq (Pair a)
|
|
|
|
derive instance ordPair ∷ Ord a ⇒ Ord (Pair a)
|
|
|
|
instance showPair ∷ Show a ⇒ Show (Pair a) where
|
|
show (x ~ y) = "(" <> show x <> " ~ " <> show y <> ")"
|
|
|
|
instance functorPair ∷ Functor Pair where
|
|
map f (x ~ y) = f x ~ f y
|
|
|
|
instance applyPair ∷ Apply Pair where
|
|
apply (f ~ g) (x ~ y) = f x ~ g y
|
|
|
|
instance applicativePair ∷ Applicative Pair where
|
|
pure x = x ~ x
|
|
|
|
instance bindPair ∷ Bind Pair where
|
|
bind (x ~ y) f = fst (f x) ~ snd (f y)
|
|
|
|
instance monadPair ∷ Monad Pair
|
|
|
|
instance semigroupPair ∷ Semigroup a ⇒ Semigroup (Pair a) where
|
|
append (x1 ~ y1) (x2 ~ y2) = (x1 <> x2) ~ (y1 <> y2)
|
|
|
|
instance monoidPair ∷ Monoid a ⇒ Monoid (Pair a) where
|
|
mempty = mempty ~ mempty
|
|
|
|
instance foldablePair ∷ Foldable Pair where
|
|
foldr f z (Pair x y) = x `f` (y `f` z)
|
|
foldl f z (Pair x y) = (z `f` x) `f` y
|
|
foldMap f (Pair x y) = f x <> f y
|
|
|
|
instance traversablePair ∷ Traversable Pair where
|
|
traverse f (Pair x y) = Pair <$> f x <*> f y
|
|
sequence (Pair mx my) = Pair <$> mx <*> my
|
|
|
|
instance distributivePair ∷ Distributive Pair where
|
|
distribute xs = map fst xs ~ map snd xs
|
|
collect f xs = map (fst <<< f) xs ~ map (snd <<< f) xs
|
|
|
|
instance arbitraryPair ∷ Arbitrary a ⇒ Arbitrary (Pair a) where
|
|
arbitrary = Pair <$> arbitrary <*> arbitrary
|