Operator precedence of =>

[Ralph Becket]

Hi,

I was hacking away t'other day, when I coded something of the form

all_p_and_q(Xs) :-
	all [X] list__member(X, Xs) => p(X), q(X).

and lawks a lordy, all Hell broke loose within negated contexts.  A
quick bit of parenthesization and we reduce to

all_p_and_q(Xs) :-
	all [X] (
		list__member(X, Xs) =>
			( p(X), q(X) )
	).

which solves the problem.  Now, I'm not sure about other people, but
I'd find it more natural (not to say, more convenient) to have the
following precedence order (from most to least tightly binding):

	conjunction < implication < quantification

rather than the current order

	implication < quantification < conjunction

I'm much in favour of the functional communities (well, ML & Haskell
types at least) dispreference for extra bracketing.

This isn't a whinge, just a POV.

Ralph

-- 
Ralph Becket  |  rwab1 at cam.sri.com  |  http://www.cam.sri.com/people/becket.html