Yes, I somewhat hacked up the rules for ! in an ad-hoc way. I really wanted to allow f !x !y = (x,y) which meant a bit of fiddling, because LHSs are parsed as terms, so this is parsed as (f ! x) ! y (ie as infix operators) and I have to squizzle around to re-interpret them as prefix operators. Not very cool. Something unified would be a Good Thing. Simon | -----Original Message----- | From: haskell-prime-bounces@haskell.org [mailto:haskell-prime- | bounces@haskell.org] On Behalf Of John Meacham | Sent: 08 July 2010 00:59 | To: haskell-prime@haskell.org | Subject: prefix operators | | It occurred to me the other day that Haskell (w/ bang patterns) now has | 3 prefix operators, all of which are defined independently and follow | their own special rules for parsing. we have (-), (!) and (~). | | It would seem to me that we should somehow be able to unify the | mechanism behind parsing these, as in practice, it seems that prefix | operators are useful in haskell. | | We have some similarities, - and ! are both infix and prefix operators, | ~ is not. ! and ~ can only be in patterns as prefix, (-) can be in both | patterns and expressions. | | But it seems like we may be able to come up with a common way of parsing | them all, prolog has had user defined infix, prefix, and postfix | operators (sharing the same name even) and is still able to parse things | properly so I don't think there will be a technical issue. | | My first impulse is to treat application as just another binary operator | with a certain precedence and find appropriate precedences for !,~,- in | the new framework. | | note: I am not proposing user defined prefix operators, just musing | about whether we can unify the rules behind parsing the current three | prefix operators, perhaps folding them into the fixity resolution | algorithm. | | John | | -- | John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/ | _______________________________________________ | Haskell-prime mailing list | Haskell-prime@haskell.org | http://www.haskell.org/mailman/listinfo/haskell-prime