On 03/02/2006, at 9:25 AM, Wolfgang Jeltsch wrote:
Am Mittwoch, 1. Februar 2006 01:32 schrieb Patryk Zadarnowski:
[...]
The proposal would be to remove the unary "-" altogether, and, instead, extend the lexical syntax of numeric constant to allow "+" and "-" prefix.
Would this mean that (-x) is a section while (-1) isn't? That would be confusing.
Apart from this, I would like to see the only unary operator of Haskell removed.
Yes, it *would* mean that (-x) and (- 1) are sections while (-1) isn't, and yes, that would be slightly confusing (and a good compiler might want to issue a warning whenever it sees a construct of the form (-identifier). However, it is NOT more confusing than what we already have with the (.) operator. Consider: (Just . not) is a perfectly reasonable function of type (Bool -> Maybe Bool) But: (Just.not) has a completely different meaning (and is probably illegal unless you have a module called "Just", which exports a function called (not).) In the case of the (.) operator, the confusion is more significant, since the meaning is context-sensitive. With the proposed "-" operator, it would be purely lexical, and therefore easy to warn about (if the compiler wishes to do so.) In both cases, accidentally omitting a space will result in a compiler or type error anyway, since (-x) has a different type than (- x), so such accidents will be picked by the compiler rather than generating invalid code. In summary: yes, the change would create *some* confusion. But much less confusion than that caused by the current treatment of (-). Pat.