On Oct 10, 2008, at 5:46 PM, Jonathan Cast wrote:
identifier = lexeme $ match "[[:lower:]_][[:alphanum:]_]*"
(pretending match :: String -> Parser String is a regex engine).
vs.
identified = lexeme $ do
c <- satisfy isLower <|> satisfy (=='_')
s <- many $ satisfy isAlphaNum <|> satisfy (=='_')
return (c:s)
lexeme $ (:) <$> (lowerChar <|> char '_') <*> (many $ alphaNum <|>
char '_') ?
or (since we're not really talking about full fledged parsers that
need lexemes here or such, but usually interpreting a single string,
otherwise regexes will quickly become atrocious)
foo (x:xs) | isLower x || x == '_', (xs', rest) <- break
alphaOrUnder xs = Just (x : xs', rest)
| otherwise = Nothing
where alphaOrUnder = liftM2 (||) isAlphaNum (=='_')
foo [] = Nothing
A bit more verbose, sure, but operating on text functionally makes it
really easy to reason about what your parser is actually doing,
unlike the mysteries of a regex.
--Sterl.
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