src/Streamly/Internal/Data/Either/Strict.hs · streamly

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streamly/src/Streamly/Internal/Data/Either/Strict.hs

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1-- |

2-- Module : Streamly.Internal.Data.Either.Strict

5-- License : BSD3

6-- Maintainer : streamly@composewell.com

7-- Stability : experimental

8-- Portability : GHC

9--

10-- | Strict data types to be used as accumulator for strict left folds and

11-- scans. For more comprehensive strict data types see

12-- https://hackage.haskell.org/package/strict-base-types . The names have been

13-- suffixed by a prime so that programmers can easily distinguish the strict

14-- versions from the lazy ones.

15--

16-- One major advantage of strict data structures as accumulators in folds and

17-- scans is that it helps the compiler optimize the code much better by

18-- unboxing. In a big tight loop the difference could be huge.

19--

20module Streamly.Internal.Data.Either.Strict

21 ( Either' (..)

22 , isLeft'

23 , isRight'

24 , fromLeft'

25 , fromRight'

26 )

27where

29-- | A strict 'Either'

30data Either' a b = Left' !a | Right' !b deriving Show

32-- | Return 'True' if the given value is a Left', 'False' otherwise.

33{-# INLINABLE isLeft' #-}

34isLeft' :: Either' a b -> Bool

35isLeft' (Left' _) = True

36isLeft' (Right' _) = False

38-- | Return 'True' if the given value is a Right', 'False' otherwise.

39{-# INLINABLE isRight' #-}

40isRight' :: Either' a b -> Bool

41isRight' (Left' _) = False

42isRight' (Right' _) = True

44-- XXX This is partial. We can use a default value instead.

45-- | Return the contents of a Left'-value or errors out.

46{-# INLINABLE fromLeft' #-}

47fromLeft' :: Either' a b -> a

48fromLeft' (Left' a) = a

49fromLeft' _ = error "fromLeft' expecting a Left'-value"

51-- | Return the contents of a Right'-value or errors out.

52{-# INLINABLE fromRight' #-}

53fromRight' :: Either' a b -> b

54fromRight' (Right' b) = b

55fromRight' _ = error "fromRight' expecting a Right'-value"