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POParsec, read text ended by a string
 

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    <p>I am struggling with <code>Parsec</code> to parse a small subset of the <a href="https://code.google.com/p/support/wiki/WikiSyntax" rel="nofollow">Google project wiki syntax</a>, and convert it into HTML. My syntax is limited to text sequences and item lists. Here is an example of what I want to recognize:</p> <pre><code>Text that can contain any kind of characters, except the string "\n *" * list item 1 * list item 2 End of list </code></pre> <p>My code so far is:</p> <pre><code>import Text.Blaze.Html5 (Html, toHtml) import qualified Text.Blaze.Html5 as H import Text.ParserCombinators.Parsec hiding (spaces) parseList :: Parser Html parseList = do items &lt;- many1 parseItem return $ H.ul $ sequence_ items parseItem :: Parser Html parseItem = do string "\n *" item &lt;- manyTill anyChar $ (try $ lookAhead $ string "\n *") &lt;|&gt; (try $ string "\n\n") return $ H.li $ toHtml item parseText :: Parser Html parseText = do text &lt;- manyTill anyChar $ (try $ lookAhead $ string "\n *") &lt;|&gt; (eof &gt;&gt; (string "")) return $ toHtml text parseAll :: Parser Html parseAll = do l &lt;- many (parseUl &lt;|&gt; parseText) return $ H.html $ sequence_ l </code></pre> <p>When applying <code>parseAll</code> to any sequence of characters, I get the following error message: <code>"*** Exception: Text.ParserCombinators.Parsec.Prim.many: combinator 'many' is applied to a parser that accepts an empty string.</code> I understand that it is because my parser <code>parseText</code> can read empty strings, but I can't see any other way. How can I recognize text delimited by a string? (<code>"\n *"</code> here).</p> <p>I am also open to any remarks or suggestions concerning the way I am using Parsec. I can't help but see that my code is a bit ugly. Can I do all this in a simpler way? For example, there is code replication (which is kind of painful) because of the string <code>"\n *"</code>, that is used to recognize the end of a text sequence, the beginning of a list item, AND the end of a list item...</p>
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    1. CODoes `sepEndBy1 (string " *" >> many (noneOf "\n")) (string "\n")` do what you want? It seems to me that is the language you are describing is just a string containing many lines started by a " *". In which case you don't even need parsec: `map (\(' ':'*':x) -> x) . lines`
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    2. COA list item could contain newlines and stars as well, the true separator for list items is "\n *".
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    3. COThe only 'illegal' sequences are strings, not chars ("\n *" and "\n\n"). That's why noneOf won't work. And I still need a way to parse text that could appear before a list.
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