[Haskell-cafe] Re: (flawed?) benchmark : sort

Denis Bueno dbueno at gmail.com
Mon Mar 10 15:20:55 EDT 2008

On Mon, Mar 10, 2008 at 3:12 PM, Neil Mitchell <ndmitchell at gmail.com> wrote:
> Hi
>  >  "The Ord class is used for totally ordered datatypes."
>  >
>  >  This *requires* that it be absolutely impossible in valid code to
>  >  distinguish equivalent (in the EQ sense, not the == sense) things via
>  >  the functions of Ord. The intended interpretation of these functions is
>  >  clear and can be taken as normative:
>  >
>  >    forall f . (compare x y == EQ and (f x or f y is defined))
>  >                   ==> f x == f y)
>  Are you sure? I would have read this as the ordering must be
>  reflexive, antisymetric and transitive - the standard restrictions on
>  any ordering. See http://en.wikipedia.org/wiki/Total_ordering

This is my reading, too.  In addition, to make it total, the property
that any two elements are comparable (this is the property that a
partial order does not necessarily have).


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