Lens.hs

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE ScopedTypeVariables #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Exception.Lens
-- Copyright   :  (C) 2012 Edward Kmett
-- License     :  BSD-style (see the file LICENSE)
-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
-- Stability   :  provisional
-- Portability :  Control.Exception
--
----------------------------------------------------------------------------
module Control.Exception.Lens
  ( exception
  ) where

import Control.Exception
import Control.Lens

-- |
-- Traverse the strongly typed 'Exception' contained in 'SomeException' where the type of your function matches
-- the desired 'Exception'.
--
-- @
-- exception :: ('Applicative' f, 'Exception' a, 'Exception' b)
--           => (a -> f b) -> 'SomeException' -> f 'SomeException'
-- @
exception :: Exception a => Simple Prism SomeException a
exception = prism toException $ \ e -> maybe (Left e) Right $ fromException e
{-# INLINE exception #-}