Question

I’m using Text.ParserCombinators.Parsec and Text.XHtml to parse an input and get a HTML output.

If my input is:

    * First item, First level
    ** First item, Second level
    ** Second item, Second level
    * Second item, First level

My output should be:

<ul><li>First item, First level <ul><li>First item, Second level </li><li>Second item, Second level </li></ul></li><li>Second item, First level</li></ul>

I wrote this, but obviously does not work recursively

list = do{ s <- many1 item;return (olist << s) }
item = do{ 
    (count 1 (char '*'))
    ;s <- manyTill anyChar newline
    ;return ( li <<  s)
  }

Any ideas?
The recursion can be more than two levels.
Thanks!

Answer 1

list n = do first <- item n
            rest <- many $ try $ try (list (n+1)) <|> item n
            return $ ulist << (first : rest)

item n = do count n (char '*')
            s <- manyTill anyChar newline
            return $ li << s

Now parse (list 1) "foo" "* a\n** a 1\n** a 2\n* b\n** b 1\n** b 2\n" will return what you asked for.

Note though, that the nested lists should themselves be inside a li, for this to be valid xhtml.