Enum on Float/Double
carette at mcmaster.ca
Tue Oct 21 15:46:00 EDT 2003
The C function you are looking for is called 'nextafter', and is present on
all systems/libraries that pretend to be fully IEEE-754 compliant (as this
is a required function from the standard). It even takes a direction
parameter (so you can do both nextafter and firstbefore). Since its API is
simple, an FFI should be rather straightforward.
From: haskell-bounces at haskell.org [mailto:haskell-bounces at haskell.org] On
Behalf Of Hal Daume III
Sent: October 21, 2003 2:37 PM
To: Ketil Z Malde
Cc: haskell at haskell.org; Simon Peyton-Jones; George Russell
Subject: Re: Enum on Float/Double
> > My preference would be for succ (+-0) to return the smallest
> > positive real, since then you could define succ x to be the unique y
> > with x < y and forall z . z < y => not (x < z), where such a y
> > exists, and I'm not sure if the Haskell standard knows about signed
> > zeros.
> Is this really useful? Why would you need this number? Peano
> artithmetic on reals? :-)
Is there any way to do this (yet)? I found a case where I really need:
f :: Float -> Float
f x is the least y such that x < y
even if i have to FFI to C, I'd really like a solution.
any help would be appreciated.
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