{- Copyright (C) 2010 Dr. Alistair Ward This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. -} {- | [@AUTHOR@] Dr. Alistair Ward [@DESCRIPTION@] * Provides impure functions to print & return the specified value. * The pure interfaces permit calls from outside the /IO-monad/. [@TODO@] Review function-names. -} module ToolShed.Unsafe( -- * Functions print', printShow ) where import qualified System.IO import qualified System.IO.Unsafe {-# NOINLINE print' #-} -- | A transparent print-function, for use in debugging. print' :: Show s => s -- ^ Arbitrary polymorphic input-data. -> s -- ^ Output (identical to input). print' = System.IO.Unsafe.unsafePerformIO . f where f :: Show s => s -> IO s f x = System.IO.hPrint System.IO.stderr x >> return {-to IO-monad-} x {-# NOINLINE printShow #-} -- | A transparent print-function, which prepends the specified label, for use in debugging. printShow :: Show s => String -- ^ The label to be printed before the value of the input data. -> s -- ^ Arbitrary polymorphic input-data. -> s -- ^ Output (identical to input). printShow label = System.IO.Unsafe.unsafePerformIO . f label where f :: Show s => String -> s -> IO s f s x = System.IO.hPutStrLn System.IO.stderr (s ++ show x) >> return {-to IO-monad-} x