--
-- Pure Haskell line/column numbers in a trace message.
--
-- Copyright 2006 Don Stewart <dons@cse.unsw.edu.au>
--
-- Free for any use.
--

module Exception (locatedError, assert) where

import qualified Control.Exception as C (catch)
import System.IO.Unsafe  (unsafePerformIO)
import GHC.Base          (assert)
import System.IO

locatedError :: Assert a -> String -> a
locatedError assrt str = unsafePerformIO $
    C.catch (assrt False $ return undefined) prettyError
    where
      prettyError e = let (x,_) = break (== ' ') $ show e
                      in error (x ++ " " ++ str)

type Assert a = Bool -> IO a -> IO a