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copied!<p>Yeah, <code>between</code> might not work for what you're looking for. Of course, for your use case, I'd follow hammar's suggestion and grab an off-the-shelf SQL parser. (personal opinion: or, try not to use SQL unless you really have to; the idea to use strings for database queries was imho a historical mistake).</p> <p><em>Note: I add an operator called <code><++></code> which will concatenate the results of two parsers, whether they are strings or characters. (code at bottom.)</em></p> <p>First, for the task of parsing parenthesis: the top level will parse some stuff between the relevant characters, which is exactly what the code says,</p> <pre><code>parseParen = char '(' <++> inner <++> char ')' </code></pre> <p>Then, the <code>inner</code> function should parse anything else: non-parens, possibly including another set of parenthesis, and non-paren junk that follows.</p> <pre><code>parseParen = char '(' <++> inner <++> char ')' where inner = many (noneOf "()") <++> option "" (parseParen <++> inner) </code></pre> <p>I'll make the assumption that for the rest of the solution, what you want to do is analgous to splitting things up by top-level SQL keywords. (i.e. ignoring those in parenthesis). Namely, we'll have a parser that will behave like so,</p> <pre><code>Main> parseTest parseSqlToplevel "select asdf(select m( 2) fr(o)m w where n) from b where delete 4" [(Select," asdf(select m( 2) fr(o)m w where n) "),(From," b "),(Where," "),(Delete," 4")] </code></pre> <p>Suppose we have a <code>parseKw</code> parser that will get the likes of <code>select</code>, etc. After we consume a keyword, we need to read until the next [top-level] keyword. The last trick to my solution is using the <code>lookAhead</code> combinator to determine whether the next word is a keyword, and put it back if so. If it's not, then we consume a parenthesis or other character, and then recurse on the rest.</p> <pre><code>-- consume spaces, then eat a word or parenthesis parseOther = many space <++> (("" <$ lookAhead (try parseKw)) <|> -- if there's a keyword, put it back! option "" ((parseParen <|> many1 (noneOf "() \t")) <++> parseOther)) </code></pre> <p>My entire solution is as follows</p> <pre><code>-- overloaded operator to concatenate string results from parsers class CharOrStr a where toStr :: a -> String instance CharOrStr Char where toStr x = [x] instance CharOrStr String where toStr = id infixl 4 <++> f <++> g = (\x y -> toStr x ++ toStr y) <$> f <*> g data Keyword = Select | Update | Delete | From | Where deriving (Eq, Show) parseKw = (Select <$ string "select") <|> (Update <$ string "update") <|> (Delete <$ string "delete") <|> (From <$ string "from") <|> (Where <$ string "where") <?> "keyword (select, update, delete, from, where)" -- consume spaces, then eat a word or parenthesis parseOther = many space <++> (("" <$ lookAhead (try parseKw)) <|> -- if there's a keyword, put it back! option "" ((parseParen <|> many1 (noneOf "() \t")) <++> parseOther)) parseSqlToplevel = many ((,) <$> parseKw <*> (space <++> parseOther)) <* eof parseParen = char '(' <++> inner <++> char ')' where inner = many (noneOf "()") <++> option "" (parseParen <++> inner) </code></pre> <h3>edit - version with quote support</h3> <p>you can do the same thing as with the parens to support quotes,</p> <pre><code>import Control.Applicative hiding (many, (<|>)) import Text.Parsec import Text.Parsec.Combinator -- overloaded operator to concatenate string results from parsers class CharOrStr a where toStr :: a -> String instance CharOrStr Char where toStr x = [x] instance CharOrStr String where toStr = id infixl 4 <++> f <++> g = (\x y -> toStr x ++ toStr y) <$> f <*> g data Keyword = Select | Update | Delete | From | Where deriving (Eq, Show) parseKw = (Select <$ string "select") <|> (Update <$ string "update") <|> (Delete <$ string "delete") <|> (From <$ string "from") <|> (Where <$ string "where") <?> "keyword (select, update, delete, from, where)" -- consume spaces, then eat a word or parenthesis parseOther = many space <++> (("" <$ lookAhead (try parseKw)) <|> -- if there's a keyword, put it back! option "" ((parseParen <|> parseQuote <|> many1 (noneOf "'() \t")) <++> parseOther)) parseSqlToplevel = many ((,) <$> parseKw <*> (space <++> parseOther)) <* eof parseQuote = char '\'' <++> inner <++> char '\'' where inner = many (noneOf "'\\") <++> option "" (char '\\' <++> anyChar <++> inner) parseParen = char '(' <++> inner <++> char ')' where inner = many (noneOf "'()") <++> (parseQuote <++> inner <|> option "" (parseParen <++> inner)) </code></pre> <p>I tried it with <code>parseTest parseSqlToplevel "select ('a(sdf'())b"</code>. cheers</p>

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