src/Streamly/Internal/Control/Exception.hs · streamly

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1-- |

2-- Module : Streamly.Internal.Control.Exception

4--

5-- License : BSD3

6-- Maintainer : streamly@composewell.com

7-- Stability : experimental

8-- Portability : GHC

9--

10-- Additional "Control.Exception" utilities.

12module Streamly.Internal.Control.Exception

13 ( assertM

14 , verify

15 , verifyM

16 )

17where

19import Control.Exception (assert)

21-- Like 'assert' but returns @()@ in an 'Applicative' context so that it can be

22-- used as an independent statement in a @do@ block.

24-- /Internal/

26{-# INLINE assertM #-}

27assertM :: Applicative f => Bool -> f ()

28assertM predicate = assert predicate (pure ())

30-- | Like 'assert' but is not removed by the compiler, it is always present in

31-- production code.

33-- /Internal/

35{-# INLINE verify #-}

36verify :: Bool -> a -> a

37verify predicate val =

38 if predicate

39 -- XXX it would be nice if we can print the predicate expr.

40 then error "verify failed"

41 else val

43-- Like 'verify' but returns @()@ in an 'Applicative' context so that it can be

44-- used as an independent statement in a @do@ block.

46-- /Internal/

48{-# INLINE verifyM #-}

49verifyM :: Applicative f => Bool -> f ()

50verifyM predicate = verify predicate (pure ())