Dylan Thurston
On Thu, Oct 25, 2001 at 10:01:57AM +0200, Ketil Malde wrote:
I think it's clear from the thread that the language designers did _not_ intend this, and that one should not use the default instances for the standard numeric classes. See Simon Peyton-Jones' recent post.
Yeah, I just read it. Unfortunately, I got this thread first :-)
I agree that Enum instances for Float/Double are not likely to be useful.
From a gut feeling, I could see a use for expressions like
[1.5, 1.6..] and [1.5, 1.6..2.0] (i.e. enumFromThen and enumFromThenTo) but enumFrom and enumFromTo making list of rounded integers seems strange to me. It seems to me that enumFromThen and -To could be implemented something like: enumFromThen beg next = beg : enumFromThen next (next+delta) where delta = next-beg similarly for enumFromThenTo, of course. i.e. depending only on functionality found in Num. Why not put these functions there, and remove Float and Double as Enum instances? What am I missing? -kzm -- If I haven't seen further, it is by standing in the footprints of giants