On 8/2/07, David Roundy <[EMAIL PROTECTED]> wrote: > This would be a very nice type to have (natural numbers), but is a tricky > type to work with. Subtraction, for instance, wouldn't be possible as a > complete function...
There is a subtraction-like operation for naturals, where a - b = 0 if a <= b. This is analogous to the way that "drop n xs" returns [] if n >= length xs, but using it in a Num instance would probably violate too many assumptions. The desire to support naturals was the motivation for including semirings in my Num refactoring thought-experiment. <http://article.gmane.org/gmane.comp.lang.haskell.cafe/15141/> _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
