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Diffstat (limited to 'src/compiler/GF/Data/BacktrackM.hs')
| -rw-r--r-- | src/compiler/GF/Data/BacktrackM.hs | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/compiler/GF/Data/BacktrackM.hs b/src/compiler/GF/Data/BacktrackM.hs index f5ae63997..87ea4dc5a 100644 --- a/src/compiler/GF/Data/BacktrackM.hs +++ b/src/compiler/GF/Data/BacktrackM.hs @@ -69,6 +69,8 @@ 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 + +instance MonadFail (BacktrackM s) where fail _ = mzero instance Functor (BacktrackM s) where |