[Haskell-cafe] Re: Parsec question (new user): unexpected end of input

29 Sep 2010


      Am 29.09.2010 11:55, schrieb Christian Maeder:
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Am 29.09.2010 09:54, schrieb Christian Maeder:
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Am 29.09.2010 05:35, schrieb Peter Schmitz:
[...]
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Error parsing file: "...\sampleTaggedContent.txt" (line 4, column 1):
unexpected end of input
expecting "<"
The input was:
[...]
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-- Parsers:
taggedContent = do
   optionalWhiteSpace
   aTag
   many tagOrContent
   aTag
"many tagOrContent" will consume all tags, so that no tag for the
following "aTag" will be left.
if you want to match a final tag, you could try:
manyTill tagOrContent (try (aTag >> eof))
better yet, avoiding backtracking, return different things for aTag and
someContents and check if the last entry is a tag.

  tagOrContent = fmap Left aTag <|> fmap Right someContent

  taggedContent = do
   spaces
   aTag
   l <- many tagOrContent
   eof
   case reverse l of
     Left _ : _ -> return ()
     _ -> fail "expected final tag before EOF"

C.
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Cheers Christian
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eof
   return "Parse complete."
tagOrContent = aTag <|> someContent  "tagOrContent"
aTag = do
   tagBegin
   xs <- many (noneOf [tagEndChar])
this also looks like "manyTill anyChar tagEnd"
C.
...
...
...
tagEnd
   optionalWhiteSpace
   return ()
someContent = do
   manyTill anyChar tagBegin
   return ()
optionalWhiteSpace = spaces   -- i.e., any of " \v\f\t\r\n"
tagBegin = char tagBeginChar
tagEnd = char tagEndChar
-- Etc:
tagBeginChar = '<'
tagEndChar = '>'
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