On Mon, Dec 13, 2004 at 07:49:00PM -0800, oleg at pobox.com wrote:
The operator ($) is often considered an application operator of a lower precedence. Modulo precedence, there seem to be no difference between ($) and `the white space', and so one can quickly get used to treat these operators as being semantically the same. However, they are not the same in all circumstances. I'd like to observe an important case where replacing the application with ($) in a fully-parenthesized expression can lead to a type error.
I think this post should go under the heading "($) considered harmful". I've been bitten by this, and I never use ($) anymore in place of parentheses because it's too tempting to think of it as syntax. (Of course, it's still useful, by itself or in a slice, as a higher-order operator.)
Andrew
I find this position ridiculous. I don't recall anyone ever posting a message about this (though I'd be far from surprised if someone did). It seems that the people who decide they need higher-rank types are capable of handling type errors involving them, and they certainly don't confuse ($) for syntax. Unless there's a realistic scenario where one suddenly decides one needs some higher-rank types and has to remove a bunch of uses of ($) but otherwise make no changes, I don't see any reason not to use ($) when you can (if you like) and not when you can't. If you ever make a mistake one way the type checker will tell you.