{-# LANGUAGE CPP             #-}
{-# LANGUAGE PatternSynonyms #-}
{-# LANGUAGE Safe            #-}
{-# LANGUAGE ViewPatterns    #-}

{-# OPTIONS_HADDOCK show-extensions #-}

-- |
-- Copyright   :  Kazuki Okamoto
-- License     :  see LICENSE
-- Maintainer  :  kazuki.okamoto@kakkun61.com
-- Stability   :  experimental
-- Portability :  GHC
--
-- A class for 1-tuples.

module Data.Tuple.Single
  ( Single (..)
  , pattern Single
  ) where

import Data.Functor.Identity (Identity (Identity, runIdentity))
import Data.Tuple.OneTuple   (OneTuple (OneTuple), only)
import Data.Tuple.Only       (Only (Only, fromOnly))

#if MIN_VERSION_ghc_prim(0,7,0)
import GHC.Tuple (Solo (Solo))
#else
import GHC.Tuple (Unit (Unit))
#endif

class Single t where
  wrap :: a -> t a
  unwrap :: t a -> a

pattern Single :: Single t => a -> t a
pattern $bSingle :: a -> t a
$mSingle :: forall r (t :: * -> *) a.
Single t =>
t a -> (a -> r) -> (Void# -> r) -> r
Single a <- (unwrap -> a) where
  Single a
a = a -> t a
forall (t :: * -> *) a. Single t => a -> t a
wrap a
a

instance Single Identity where
  wrap :: a -> Identity a
wrap = a -> Identity a
forall a. a -> Identity a
Identity
  unwrap :: Identity a -> a
unwrap = Identity a -> a
forall a. Identity a -> a
runIdentity

{-# COMPLETE Single :: Identity #-}

instance Single Only where
  wrap :: a -> Only a
wrap = a -> Only a
forall a. a -> Only a
Only
  unwrap :: Only a -> a
unwrap = Only a -> a
forall a. Only a -> a
fromOnly

{-# COMPLETE Single :: Only #-}

instance Single OneTuple where
  wrap :: a -> OneTuple a
wrap = a -> OneTuple a
forall a. a -> OneTuple a
OneTuple
  unwrap :: OneTuple a -> a
unwrap = OneTuple a -> a
forall a. OneTuple a -> a
only

{-# COMPLETE Single :: OneTuple #-}

#if MIN_VERSION_ghc_prim(0,7,0)
instance Single Solo where
  wrap = Solo
  unwrap (Solo a) = a

{-# COMPLETE Single :: Solo #-}
#else
instance Single Unit where
  wrap :: a -> Unit a
wrap = a -> Unit a
forall a. a -> Unit a
Unit
  unwrap :: Unit a -> a
unwrap (Unit a
a) = a
a

{-# COMPLETE Single :: Unit #-}
#endif