On 03:53 Thu 15 Apr , rocon...@theorem.ca wrote: > On Wed, 14 Apr 2010, Ashley Yakeley wrote: > > > On 2010-04-14 14:58, Ashley Yakeley wrote: > >> On 2010-04-14 13:59, rocon...@theorem.ca wrote: > >> > >>> There is some notion of value, let's call it proper value, such that > >>> bottom is not one. > >>> > >>> In other words bottom is not a proper value. > >>> > >>> Define a proper value to be a value x such that x == x. > >>> > >>> So neither undefined nor (0.0/0.0) are proper values > >>> > >>> In fact proper values are not just subsets of values but are also > >>> quotients. > >>> > >>> thus (-0.0) and 0.0 denote the same proper value even though they are > >>> represented by different Haskell values. > >> > >> The trouble is, there are functions that can distinguish -0.0 and 0.0. > >> Do we call them bad functions, or are the Eq instances for Float and > >> Double broken? > > I'd call them disrespectful functions, or maybe nowadays I might call them > improper functions. The "good" functions are respectful functions or > proper functions.
<snip from other post> > Try using the (x == y) ==> (f x = g y) test yourself. Your definitions seem very strange, because according to this, the functions f :: Double -> Double f x = 1/x and g :: Double -> Double g x = 1/x are not equal, since (-0.0 == 0.0) yet f (-0.0) /= g (0.0). -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
