If naturals have a perfectly reasonable subtraction then they also have a perfectly reasonable negate; the default is 0-x.
(Oh, subtraction wasn't THAT reasonable, you say. :) ) -- Lennart On 10/17/07, John Meacham <[EMAIL PROTECTED]> wrote: > > 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 > > >operator. > > > > 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 > negate. > > 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 > > > -- > John Meacham - ⑆repetae.net⑆john⑈ > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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