[Haskell-cafe] Strange subtract operator behavior
john at repetae.net
Tue Oct 16 21:10:51 EDT 2007
On Tue, Oct 16, 2007 at 06:27:19PM -0300, Isaac Dupree wrote:
> Peter Verswyvelen wrote:
> >Personally I could also live with allowing no space between the minus
> >sign and the number... If you leave a space, - becomes the subtract
> I once thought that... there was the opposition that (x-1) subtraction
> of a constant appears too often. And I found that I myself wrote that
> several times. And saying "whitespace on the left but not the right"
> seems too complicated for Haskell lexer semantics. So the current
> situation is just unhappy, that's all. (and maybe compiler warnings
> could still be implemented)
not just unhappy, but inefficient.
-10 tranlates to (negate (fromInteger 10)) requiring 2 indirect class
calls rather than what one might expect (fromInteger -10)
also, negate in Num is sort of ugly IMHO. It would be nice if it wern't
there. Things like naturals have a perfectly reasonable subtract, but no
I think losing x-1 would be worth it. but I know there were some other
ideas out there that might be preferable but could still be handled at
the lexing stage rather than the parsing one...
John Meacham - ⑆repetae.net⑆john⑈
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