On 6/21/07, Dave Tapley <[EMAIL PROTECTED]> wrote:
> primary = (identifier >>= (return . PrimaryIdentifier)) <|> (stringLiteral >>= (return . PrimaryLiteral)) > identifier = (many1 letter) >>= (return . Identifier) > stringLiteral = (char '\'') >> (manyTill anyChar (char '\'')) >>= (return . StringLiteral)
I have found this a sufficiently common pattern that I have a little combinator to tidy it up: p `with` f = p >>= (return . f) so I can write primary = (identifier `with` PrimaryIdentifier) <|> (stringLiteral `with` PrimaryLiteral) Obviously you could write it in terms of liftM, choose a different name, &c, &c. FWIW, the other little combinator I invariably use is p `returning` x = p >>= (\_ -> return x) which I end up calling with () as the second argument so often (especially during development), I usually have another combinator void p = p >> return () YMMV, T. -- Dr Thomas Conway [EMAIL PROTECTED] Silence is the perfectest herald of joy: I were but little happy, if I could say how much. _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
