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| author | aarne <aarne@cs.chalmers.se> | 2008-06-25 16:54:35 +0000 |
|---|---|---|
| committer | aarne <aarne@cs.chalmers.se> | 2008-06-25 16:54:35 +0000 |
| commit | e9e80fc389365e24d4300d7d5390c7d833a96c50 (patch) | |
| tree | f0b58473adaa670bd8fc52ada419d8cad470ee03 /src/GF/Data/ErrM.hs | |
| parent | b96b36f43de3e2f8b58d5f539daa6f6d47f25870 (diff) | |
changed names of resource-1.3; added a note on homepage on release
Diffstat (limited to 'src/GF/Data/ErrM.hs')
| -rw-r--r-- | src/GF/Data/ErrM.hs | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/src/GF/Data/ErrM.hs b/src/GF/Data/ErrM.hs new file mode 100644 index 000000000..e8cea12d4 --- /dev/null +++ b/src/GF/Data/ErrM.hs @@ -0,0 +1,38 @@ +---------------------------------------------------------------------- +-- | +-- Module : ErrM +-- Maintainer : AR +-- Stability : (stable) +-- Portability : (portable) +-- +-- > CVS $Date: 2005/04/21 16:22:00 $ +-- > CVS $Author: bringert $ +-- > CVS $Revision: 1.5 $ +-- +-- hack for BNFC generated files. AR 21/9/2003 +----------------------------------------------------------------------------- + +module GF.Data.ErrM (Err(..)) where + +import Control.Monad (MonadPlus(..)) + +-- | like @Maybe@ type with error msgs +data Err a = Ok a | Bad String + deriving (Read, Show, Eq) + +instance Monad Err where + return = Ok + fail = Bad + Ok a >>= f = f a + Bad s >>= f = Bad s + +-- | added 2\/10\/2003 by PEB +instance Functor Err where + fmap f (Ok a) = Ok (f a) + fmap f (Bad s) = Bad s + +-- | added by KJ +instance MonadPlus Err where + mzero = Bad "error (no reason given)" + mplus (Ok a) _ = Ok a + mplus (Bad s) b = b |
