[Vm-dev] Signed/unsigned shifting
Ben Coman
btc at openInWorld.com
Thu Nov 27 08:52:51 UTC 2014
Nicolas Cellier wrote:
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> ------------------------------------------------------------------------
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> 2014-11-23 0:56 GMT+01:00 Ben Coman <btc at openinworld.com
> <mailto:btc at openinworld.com>>:
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> Chris Muller wrote:
>
> On Sat, Nov 22, 2014 at 10:12 AM, Eliot Miranda
> <eliot.miranda at gmail.com <mailto:eliot.miranda at gmail.com>> wrote:
>
> Hi Bert,
>
> On Sat, Nov 22, 2014 at 5:12 AM, Bert Freudenberg
> <bert at freudenbergs.de <mailto:bert at freudenbergs.de>> wrote:
>
>
> On 21.11.2014, at 23:01, Eliot Miranda uploaded
> VMMaker.oscog-eem.950.mcz
>
> Introduce >>> as an explicitly signed shift.
>
> Ugh, can we pick something else, please? It's really
> confusing. In various languages (notably Java and
> JavaScript), >> is signed and >>> unsigned. I don't know
> any language that has both operators and the meaning
> reversed.
>
>
> This is confused because of history. What I'd like is to
> use >> as a signed shift (because that's what it is) and >>>
> as an unsigned shift. And I'd like to change bitShift: to
> generate signed shifts and introduce unsignedBitShift: and
> ditch signedBitShift:. But that means changing all uses of
> >> in VMMaker. This would be my preferred solution but I
> think its *really* important that if we go this route we
> change VMMaker.oscog, VMMaker and VMMakerJS at the same
> time. Can we synchronise this?
>
>
>
> And >> still means signed or unsigned depending on
> context. Not nice at all.
>
>
> Right. And there's the signedBitShift: bogosity too.
>
>
> How about ...
>
> >> signed/unsigned depending on type (what we
> have now)
> >>+ force unsigned shift
> >>- force signed shift
>
>
> That's funny. For me the + screams signed.
>
>
> Berts made more sense to me simply because signed support
> negatives(-), where unsigned only support positive(+)..
>
>
> Revising my previous suggestion...
> >>> force unsigned
> >>- force signed
>
> cheers -ben
>
>
> As a latin, writing the most significant bit to least significant from
> left to right, and the sign leftmost, I would suggest ->> to suggest how
> we propagate the minus sign bit...
>
> Nicolas
Interesting point.
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