half datatype?

[Manu]

On 19 November 2012 19:28, Iain Buclaw <ibuclaw at ubuntu.com> wrote:

> On 19 November 2012 16:04, Manu <turkeyman at gmail.com> wrote:
> > On 19 November 2012 06:19, Walter Bright <newshound2 at digitalmars.com>
> wrote:
> >>
> >> On 11/18/2012 4:31 PM, Manu wrote:
> >>>
> >>> If I told you this is how real should be implemented, would you vote
> ++?
> >>> What
> >>> about double? Why?
> >>> Why not float for that matter? There seems like no reason for the
> >>> language to
> >>> define any floating point type at all if you consider this
> acceptable...
> >>
> >>
> >> Because they are implemented in hardware. It's pretty dang hard for a
> >> compiler to look at a floating point emulator and figure out "gee, I
> have a
> >> nice hardware instruction that does the same thing as this 2K of code!"
> >
> >
> > Right, and this is my point precisely. It's hard for GDC for instance to
> > hook some complex library because it happens to have hardware to do it.
> >
> >>> 'half' isn't some custom float for niche use, it's an established
> >>> standard,
> >>> implemented in vastly more hardware than implements 'real'.
> >>
> >>
> >> It's implemented in GPUs, sure, but it is it implemented in hardware
> that
> >> D runs on? (I do know about this:
> >> http://gcc.gnu.org/onlinedocs/gcc/Half_002dPrecision.html)
> >>
> >> There is no major technical difficulty in implementing it as a basic
> type,
> >> but I want to be sure we've exhausted the library approach first.
> >
> >
> > Well it's available in hardware on basically all mobile devices (that's a
> > LOT of devices (in the billions)), but even if it's just implemented in
> > software (x86), the values are consumed by the GPU, and the validity of
> the
> > values is no less important. It still seems like a valuable 1st class
> type;
> > why shouldn't it enjoy the same casting, assignment, literal, range
> checking
> > rules as the rest of the floats? Additionally, convenience and
> compatibility
> > with generic code would be significantly improved.
> > I don't see how it can be made to feel seamless with a lib... and that
> > sounds like an awful lot more work.
> >
> >
> > Anyway, I'm not desperate for this personally. I just wondered how people
> > felt about it in general, and if it was something that should/would be
> > seriously considered.
>
> I'm neither here nor there.  I'm just pointing out that you are
> proposing a dedicated type to be introduced that is supported on only
> one platform. :-)
>

real is only supported on one platform (x86, it's deprecated in x64 and x87
will likely be removed/emulated in the future), but I think many here
consider it valuable(?).
And that's not strictly true either, virtually every machine has a GPU, and
host software still has to process data for it. I'm mainly encouraging this
for the sake of correctness/type safety, though hardware support on ARM
would be a particularly nice bonus.

I also wanted to gauge the interest/opposition.
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