"Michael Shulman"
A propos of sections of subtraction, and thence to sections of other noncommutative operators, as a Haskell newbie I was surprised to discover (the hard way!) that
(< 0)
and
((<) 0)
mean different things. I had typed (< 0) when I meant to type ((<) 0). No compiler errors, of course, and I had a devil of a time finding that bug. My initial reaction was that (< 0) should be an error and you should have to write ((>) 0); now I realize that the section notation is more fundamental, since (<) itself is actually a "double section". And of course I should have written (> 0) anyway;
Well, this is the first time I've noticed anyone mention it! If you appreciate sections, you read (< 0) as "less than zero", and the meaning is clear. I don't think it takes much in the way of mental gymnastics to do that, since you just read the tokens in order.
it's probably my lisp background that tripped me up.
I should think so. But does lisp have currying these days? (lessp 0 1) ==> T but (lessp 0) would be an error, wouldn't it?
But is there any way this could be made less confusing?
Right about the start of the design of Haskell, I proposed the rule "parentheses should only be used for grouping". If we had adopted that, you wouldn't have been confused by sections, because sections would have had to use a different syntax. However, while I was reluctant to lose the rule, sections in their present form do have a great deal to be said for them. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2006-09-07)