ab416326ad
Previously it was a tuple, which meant it couldn't have sensible custom instances. Token and TokenType now have Show instances, so we get more useful output when parsing fails.
88 lines
3.4 KiB
Haskell
88 lines
3.4 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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-- | Analyse syntactic structure of occam code.
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module StructureOccam (structureOccam) where
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import Errors
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import LexOccam
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import Metadata
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import Pass
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-- | Reserved words that, if found at the end of a line, indicate the next
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-- line is a continuation.
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continuationWords :: [String]
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continuationWords
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= [ "-", "~", "+", "-", "*", "/", "\\", "/\\", "\\/", "><", "=", "<>",
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"<", ">", ">=", "<=", ",", ";", ":=", "<<", ">>",
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"AFTER", "AND", "BITAND", "BITNOT", "BITOR", "FOR", "FROM",
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"IS", "MINUS", "MINUS", "NOT", "OR", "PLUS", "REM", "RESHAPES",
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"RETYPES", "SIZE", "TIMES" ]
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-- | Given the output of the lexer for a single file, add `Indent`, `Outdent`
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-- and `EndOfLine` markers.
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structureOccam :: [Token] -> PassM [Token]
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structureOccam [] = return []
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structureOccam ts = analyse 1 firstLine ts (Token emptyMeta EndOfLine)
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where
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-- Find the first line that's actually got something on it.
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firstLine
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= case ts of ((Token m _):_) -> metaLine m
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analyse :: Int -> Int -> [Token] -> Token -> PassM [Token]
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-- Add extra EndOfLine at the end of the file.
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analyse prevCol _ [] _ = return $ Token emptyMeta EndOfLine : out
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where out = replicate (prevCol `div` 2) (Token emptyMeta Outdent)
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analyse prevCol prevLine (t@(Token m tokType):ts) prevTok
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| line /= prevLine && not isContinuation
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= do rest <- analyse col line ts t
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newLine $ t : rest
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| otherwise
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= do rest <- analyse prevCol line ts t
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return $ t : rest
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where
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col = metaColumn m
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line = metaLine m
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isContinuation = case prevTok of
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Token _ (TokReserved s) ->
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s `elem` continuationWords
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Token _ (TokStringCont _) -> True
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_ -> False
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-- A new line -- look to see what's going on with the indentation.
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newLine :: [Token] -> PassM [Token]
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newLine rest
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| col == prevCol + 2 = withEOL $ Token m Indent : rest
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-- FIXME: If col > prevCol, then look to see if there's a VALOF
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-- coming up before the next column change...
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| col < prevCol
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= if (prevCol - col) `mod` 2 == 0
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then withEOL $ replicate steps (Token m Outdent) ++ rest
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else bad
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| col == prevCol = withEOL rest
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| otherwise = bad
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where
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steps = (prevCol - col) `div` 2
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bad :: PassM [Token]
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bad = dieP m "Invalid indentation"
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-- This is actually the position at which the new line starts
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-- rather than the end of the previous line.
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withEOL ts = return $ Token m EndOfLine : ts
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