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copied!<p>If you can factor <code>parser1</code> so that is defined like so:</p> <pre><code>parser1 = (try parser2) <|> parser1extra </code></pre> <p>Then the problem becomes a list of <code>parser1extra</code> or <code>parser2</code> that must end in the later. You can code that as:</p> <pre><code>parserList = liftM2 (:) (try parser1extra) parserList <|> liftM2 (:) (try parser2) (option [] parserList) </code></pre> <p>You may or may not need the <code>try</code> calls depending on if those parsers have any prefix overlap.</p> <p>If you don't want the return value to be a list, but instead your AParse datum, then you could re-write it this way:</p> <pre><code>parserList = do a <- try parser1extra prefix a parserList <|> do a <- try parser2 option (AParse [] a) (prefix a parserList) where prefix a p = do (AParse as t) <- p return $ (AParse (a:as) t) </code></pre> <p>Or, a full example:</p> <pre><code>import Control.Monad import Text.ParserCombinators.Parsec parseNum = do { v <- many1 digit; spaces; return v } parseWord = do { v <- many1 letter; spaces; return v } parsePart = parseNum <|> parseWord parsePartListEndingInWord = liftM2 (:) (try parseNum) parsePartListEndingInWord <|> liftM2 (:) (try parseWord) (option [] parsePartListEndingInWord) </code></pre> <p>Actually, the calls to try aren't needed in this case, as <code>parseNum</code> and <code>parseWord</code> match no common prefix. Notice that <code>parsePartListEndingInWord</code> doesn't actually reference <code>parsePart</code>, but instead, the two options that make up <code>parsePart</code>'s definition</p> <hr> <p>(Original answer, solving a somewhat different situation:)</p> <p>How about something like:</p> <pre><code>parserTest = between (char '[') (char ']') $ do p1s <- try parser1 `endBy` char ',' p2 <- parser2 return $ AParse p1s p2 </code></pre> <p>Taking the punctuation out of your parsers and up into parseTest allows you to use the combinators <code>between</code> and <code>endBy</code> to do the work for you. Lastly, the <code>try</code> is there so that if <code>parser1</code> and <code>parser2</code> match a common prefix, <code>endBy</code> will perform the correct full backup to beginning of the common prefix.</p> <p>Depending on your parsers, it is possible that you can leave the punctuation matching inside your sub-parsers, and all you need might be the a <code>try</code> around <code>parser1</code>:</p> <pre><code>parseTest = do parse1 <- many (try parser1) parse2 <- parser2 return AParse parse1 parse2 </code></pre>

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