[Haskell-cafe] Re: A question about "monad laws"

Wilhelm B. Kloke wrote:

ajb@spamcop.net schrieb:

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G'day all.

Richard A. O'Keefe wrote:

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Hmm. Personally, I've never seen an algorithm where comparing for exact equality was algorithmically necessary.

One trick I've occasionally used is to avoid the need for a discriminated union of floating point and integer types by just using a floating point number.

IMHO it is a perfectly good idea to use the FP processor for integer computations. You can use the Inexact Trap as Overflow Exception, a service you don't get from i386 (and most other) hardware for int operations. Of course your integers are limited to 24bit+sign in single precision and 54bit+sign in double. In i387 extended precision you get 64bit+sign.

I would consider a good idea if ghc would provide language support to this sort of integers.

No need, you can do that for yourself: {-# LANGUAGE GeneralizedNewtypeDeriving #-} newtype DInt = DInt Double deriving (Eq, Ord, Enum, Num) instance Show DInt where show (DInt x) = show (truncate x :: Integer) You can even make it H98 by defining the instances manually... Cheers Ben