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| author | krangelov <kr.angelov@gmail.com> | 2020-10-02 19:55:24 +0200 |
|---|---|---|
| committer | krangelov <kr.angelov@gmail.com> | 2020-10-02 19:55:24 +0200 |
| commit | f3a8658cc1ed5b2721ee9d3f670f6b9a49f0f049 (patch) | |
| tree | 8a311ec3c3a454088fa3c74b4464f974fe5aee21 /src/compiler/GF/Data/BacktrackM.hs | |
| parent | bfb94d1e48fded159bbf63a992564cb24e987772 (diff) | |
| parent | f56fbcf86e472262d07c6bd713f6955cfbcfee8a (diff) | |
Merge branch 'master' of https://github.com/GrammaticalFramework/gf-core
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 |