diff options
| author | John J. Camilleri <john@johnjcamilleri.com> | 2020-09-14 22:42:37 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-09-14 22:42:37 +0200 |
| commit | 6c54e5b63cb563d780843a1970cba0718a5203f8 (patch) | |
| tree | ed6777f6cb20f9212fa29ce68fac7e22745c707c /src/compiler/GF/Data/BacktrackM.hs | |
| parent | bca0691cb028fe33ae1b77e71752d4e937490ff1 (diff) | |
| parent | 8bcdeedba01847325cc89378fed114bc0561bd4d (diff) | |
Merge pull request #71 from anka-213/fix-newer-cabal
Fix support for newer stackage snapshots
Diffstat (limited to 'src/compiler/GF/Data/BacktrackM.hs')
| -rw-r--r-- | src/compiler/GF/Data/BacktrackM.hs | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/compiler/GF/Data/BacktrackM.hs b/src/compiler/GF/Data/BacktrackM.hs index f5ae63997..14cbf90d2 100644 --- a/src/compiler/GF/Data/BacktrackM.hs +++ b/src/compiler/GF/Data/BacktrackM.hs @@ -13,6 +13,7 @@ ----------------------------------------------------------------------------- {-# LANGUAGE Rank2Types, MultiParamTypeClasses, FlexibleInstances #-} +{-# LANGUAGE CPP #-} module GF.Data.BacktrackM ( -- * the backtracking state monad BacktrackM, @@ -32,6 +33,7 @@ import Data.List import Control.Applicative import Control.Monad import Control.Monad.State.Class +import qualified Control.Monad.Fail as Fail ---------------------------------------------------------------------- -- Combining endomorphisms and continuations @@ -69,6 +71,12 @@ instance Monad (BacktrackM s) where return a = BM (\c s b -> c a s b) BM m >>= k = BM (\c s b -> m (\a s b -> unBM (k a) c s b) s b) where unBM (BM m) = m + +#if !(MIN_VERSION_base(4,13,0)) + fail = Fail.fail +#endif + +instance Fail.MonadFail (BacktrackM s) where fail _ = mzero instance Functor (BacktrackM s) where |