92 lines
3.5 KiB
Haskell
92 lines
3.5 KiB
Haskell
{-
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Tock: a compiler for parallel languages
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Copyright (C) 2007 University of Kent
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This program is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 2 of the License, or (at your
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option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program. If not, see <http://www.gnu.org/licenses/>.
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-}
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-- | Error handling and reporting.
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module Errors (checkJust, Die, dieInternal, dieIO, dieP, dieReport, ErrorReport) where
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import Control.Monad.Error
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import Control.Monad.Trans
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import Data.List
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import System.IO.Error
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import Metadata
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type ErrorReport = (Maybe Meta, String)
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instance Error ErrorReport where
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strMsg s = (Nothing, s)
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-- | Class of monads that can fail.
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class Monad m => Die m where
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dieReport :: ErrorReport -> m a
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-- | Fail, giving a position and an error message.
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dieP :: Die m => Meta -> String -> m a
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dieP m s = dieReport (Just m,s)
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-- | Wrapper around error that gives nicer formatting, and prints out context
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--
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dieIO :: (Monad m, MonadIO m) => ErrorReport -> m a
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dieIO (Just m@(Meta (Just fn) line column),s) = liftIO $
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-- If we can't read the file successfully, still print our original error
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-- rather than a "can't read file" error:
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do fileContents <- catch (readFile fn) (\_ -> printError s)
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let startingLine = max 1 (line - contextLines)
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let lines = map replaceTabs $ getLines fileContents (startingLine) ((2 * contextLines) + 1)
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putStrLn $ fn ++ ":"
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printLines startingLine (take (line - startingLine + 1) lines)
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putStr "Here"
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replicateM_ column (putChar '-') -- column is unit-based, but we want an extra dash anyway
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putStrLn "^"
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printLines (line + 1) (drop (line - startingLine + 1) lines)
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putStrLn ""
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printError $ (show m) ++ " " ++ s
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where
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contextLines :: Int
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contextLines = 5
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-- start is unit-based, so we need to convert to zero-based
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getLines :: String -> Int -> Int -> [String]
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getLines all start total = take total (drop (start - 1) (lines all))
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printLines :: Int -> [String] -> IO ()
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printLines n lines = mapM_ (\(n,s) -> (putStrLn . ((++) (justify5 n) )) s) (zip [n..] lines)
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--Makes sure line number and colon are exactly 5 characters long:
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justify5 :: Int -> String
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justify5 num = if n <= 4 then s ++ ":" ++ (replicate (4 - n) ' ') else "x" ++ (drop (n - 3) s) ++ ":"
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where
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s = show num
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n = length s
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-- Replace tabs with eight spaces, to match alex:
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replaceTabs :: String -> String
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replaceTabs [] = []
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replaceTabs ('\t':ss) = (replicate 8 ' ') ++ replaceTabs ss
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replaceTabs (s:ss) = (s : replaceTabs ss)
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dieIO (_,s) = printError s
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printError :: String -> a
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printError s = error $ "Error: " ++ s ++ "\n"
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-- | Fail after an internal error.
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dieInternal :: Monad m => ErrorReport -> m a
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dieInternal (m,s) = error $ "\n\n" ++ (maybe "" show m) ++ "Internal error: " ++ s
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-- | Extract a value from a Maybe type, dying with the given error if it's Nothing.
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checkJust :: Die m => ErrorReport -> Maybe t -> m t
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checkJust _ (Just v) = return v
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checkJust err _ = dieReport err
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