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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE TypeSynonymInstances #-}
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------------------------------------------------------------------------------
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-- | Wrapper for Control.Monad.Except from the mtl package
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------------------------------------------------------------------------------
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module Agda.Utils.Except
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( Error(noMsg, strMsg)
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, MonadError(catchError, throwError)
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------------------------------------------------------------------------
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#if MIN_VERSION_mtl(2,2,1)
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-- New mtl, reexport ExceptT, define class Error for backward compat.
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------------------------------------------------------------------------
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import Control.Monad.Except
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-- | We cannot define data constructors synonymous, so we define the
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-- @mkExceptT@ function to be used instead of the data constructor
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mkExceptT :: m (Either e a) -> ExceptT e m a
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-- From Control.Monad.Trans.Error of transformers 0.3.0.0.
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-- | A string can be thrown as an error.
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instance Error String where
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------------------------------------------------------------------------
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-- Old mtl, need to define ExceptT from ErrorT
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------------------------------------------------------------------------
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import Control.Monad.Error
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-- | We cannot define data constructors synonymous, so we define the
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-- @mkExceptT@ function to be used instead of the data constructor
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mkExceptT :: m (Either e a) -> ExceptT e m a
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-- | 'runExcept' function using mtl 2.1.*.
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runExceptT :: ExceptT e m a -> m (Either e a)
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runExceptT = runErrorT
added
removed
src/full/Agda/Utils/Except.hs
