* [Caml-list] Finding the sign of a float
@ 2003-02-01 6:35 Shawn Wagner
2003-02-01 9:05 ` Chris Hecker
2003-02-01 12:56 ` John Carr
0 siblings, 2 replies; 5+ messages in thread
From: Shawn Wagner @ 2003-02-01 6:35 UTC (permalink / raw)
To: caml-list
I'm looking for a way, in pure ocaml without having to bail out to C, to
tell if a float is negative or not.
Just using x < 0.0 won't work, as I need to be able to tell the difference
between -0.0 and +0.0. This is for ocaml versions of the C copysign and
signbit functions. Any suggestions?
--
Shawn Wagner
shawnw@speakeasy.org
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Caml-list] Finding the sign of a float
2003-02-01 6:35 [Caml-list] Finding the sign of a float Shawn Wagner
@ 2003-02-01 9:05 ` Chris Hecker
2003-02-01 12:56 ` John Carr
1 sibling, 0 replies; 5+ messages in thread
From: Chris Hecker @ 2003-02-01 9:05 UTC (permalink / raw)
To: Shawn Wagner, caml-list
>I'm looking for a way, in pure ocaml without having to bail out to C, to
>tell if a float is negative or not.
>Just using x < 0.0 won't work, as I need to be able to tell the difference
>between -0.0 and +0.0. This is for ocaml versions of the C copysign and
>signbit functions. Any suggestions?
let is_neg v =
(Int64.shift_right_logical (Int64.bits_of_float v) 63) = Int64.one
Chris
PS. My kingdom for overloaded arithmetic operators and Int32/64 constants.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Caml-list] Finding the sign of a float
2003-02-01 6:35 [Caml-list] Finding the sign of a float Shawn Wagner
2003-02-01 9:05 ` Chris Hecker
@ 2003-02-01 12:56 ` John Carr
2003-02-01 14:11 ` malc
1 sibling, 1 reply; 5+ messages in thread
From: John Carr @ 2003-02-01 12:56 UTC (permalink / raw)
To: Shawn Wagner; +Cc: caml-list
> I'm looking for a way, in pure ocaml without having to bail out to C, to
> tell if a float is negative or not.
>
> Just using x < 0.0 won't work, as I need to be able to tell the difference
> between -0.0 and +0.0. This is for ocaml versions of the C copysign and
> signbit functions. Any suggestions?
x < 0.0 || (x = 0.0 && 1.0/.x < 0.0)
may be faster than converting the bits to integer, or slower,
depending on platform and context, and how often you encounter -0.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Caml-list] Finding the sign of a float
2003-02-01 12:56 ` John Carr
@ 2003-02-01 14:11 ` malc
2003-02-01 18:05 ` Shawn Wagner
0 siblings, 1 reply; 5+ messages in thread
From: malc @ 2003-02-01 14:11 UTC (permalink / raw)
To: John Carr; +Cc: Shawn Wagner, caml-list
On Sat, 1 Feb 2003, John Carr wrote:
>
> > I'm looking for a way, in pure ocaml without having to bail out to C, to
> > tell if a float is negative or not.
> >
> > Just using x < 0.0 won't work, as I need to be able to tell the difference
> > between -0.0 and +0.0. This is for ocaml versions of the C copysign and
> > signbit functions. Any suggestions?
>
> x < 0.0 || (x = 0.0 && 1.0/.x < 0.0)
>
> may be faster than converting the bits to integer, or slower,
> depending on platform and context, and how often you encounter -0.
1.0 /. x = neg_infinity less typing
--
mailto:malc@pulsesoft.com
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Caml-list] Finding the sign of a float
2003-02-01 14:11 ` malc
@ 2003-02-01 18:05 ` Shawn Wagner
0 siblings, 0 replies; 5+ messages in thread
From: Shawn Wagner @ 2003-02-01 18:05 UTC (permalink / raw)
To: caml-list
On Sat, Feb 01, 2003 at 05:11:10PM +0300, malc wrote:
> On Sat, 1 Feb 2003, John Carr wrote:
>
> >
> > > I'm looking for a way, in pure ocaml without having to bail out to C, to
> > > tell if a float is negative or not.
> > >
> > > Just using x < 0.0 won't work, as I need to be able to tell the difference
> > > between -0.0 and +0.0. This is for ocaml versions of the C copysign and
> > > signbit functions. Any suggestions?
> >
> > x < 0.0 || (x = 0.0 && 1.0/.x < 0.0)
> >
> > may be faster than converting the bits to integer, or slower,
> > depending on platform and context, and how often you encounter -0.
>
> 1.0 /. x = neg_infinity less typing
>
That one doesn't work for all negative numbers, though. I think I'll go
with John's, though Chris's suggestion of converting to an int64 is nifty. I
wasn't aware of bits_to_float before.
PS: I agree with Chris's sentiments about overloaded arithmetic operators
(It has to be possible; < > and = do it...) and largeint constants. That
last one is particularily annoying, as I never could figure out how to make
my patch to add them work with camlp4.
--
Shawn Wagner
shawnw@speakeasy.org
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2003-02-01 9:05 ` Chris Hecker
2003-02-01 12:56 ` John Carr
2003-02-01 14:11 ` malc
2003-02-01 18:05 ` Shawn Wagner
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