bit shift

bit shift

[Stephen Frackelton]

does a bit shift operation / mechanism exist in ada83 ?
i'm doing some checksum algorithm work and want to cyclically rotate bits a
number of places within a word.

Re: bit shift

[Jim Rogers]

Look in the package Interfaces.
That package contains the functions
Shift_Left
Shift_Right
Shift_Right_Arithmetic
Rotate_Left
Rotate_Right

Jim Rogers

Stephen Frackelton wrote:

> does a bit shift operation / mechanism exist in ada83 ?
> i'm doing some checksum algorithm work and want to cyclically rotate bits a
> number of places within a word.
> 
> 
> 
> 

A Interfaces package for '83?

[Petter Fryklund]

Is there really any?

Re: bit shift

[John McCabe]

On Mon, 25 Feb 2002 14:03:32 -0000, "Stephen Frackelton"
<stephen.frackelton@baesystems.com> wrote:

>does a bit shift operation / mechanism exist in ada83 ?
>i'm doing some checksum algorithm work and want to cyclically rotate bits a
>number of places within a word.

There is nothing defined in the Ada 83 LRM to provide this facility
directly, but there is often a package provided by your compiler
vendor that will do it. In TLD Mil-Std-1750A compiler there was a
package called (I think) BITS. Look in your compiler documentation and
you may find something.

As a matter of interest, what compiler are you using?

Re: bit shift

[Robert Dewar]

"Stephen Frackelton" <stephen.frackelton@baesystems.com> wrote in message news:<3c7a442c$1@pull.gecm.com>...
> does a bit shift operation / mechanism exist in ada83 ?
> i'm doing some checksum algorithm work and want to
> cyclically rotate bits a
> number of places within a word.

No it does not, ignore the answer you got from 
Jim Rogers, he ignored the ada83 in your question.

Not that I blame him, at this stage, seven years after
the Ada 95 standard has been issued, it seems a pity
that anyone has to struggle with the use of an obsolete
language :-)

Re: bit shift

[Ted Dennison]

Jim Rogers <jimmaureenrogers@worldnet.att.net> wrote in message news:<3C7A5391.60206@worldnet.att.net>...
> Look in the package Interfaces.

...which doesn't exist for Ada83, I'm afraid.

> Stephen Frackelton wrote:
> 
> > does a bit shift operation / mechanism exist in ada83 ?

---
T.E.D.

Re: bit shift

[Jim Rogers]

Right. I did overlook the Ada83 bit. I must get my new
prescription filled for my glasses.

You can implement a Right_Shift by dividing by multiples of
2. This does, however, require that the value being shifted
is an integer type. That is the most common situation for
bit shifting.

Left shifting becomes a significant problem using a signed
integer.

Jim Rogers

Ted Dennison wrote:

> Jim Rogers <jimmaureenrogers@worldnet.att.net> wrote in message news:<3C7A5391.60206@worldnet.att.net>...
> 
>>Look in the package Interfaces.
>>
> 
> ...which doesn't exist for Ada83, I'm afraid.
> 
> 
>>Stephen Frackelton wrote:
>>
>>
>>>does a bit shift operation / mechanism exist in ada83 ?
>>>
> 
> ---
> T.E.D.
> 

Re: bit shift

[Frank J. Lhota]

"Jim Rogers" <jimmaureenrogers@worldnet.att.net> wrote in message
news:3C7A5391.60206@worldnet.att.net...
> Look in the package Interfaces.
> That package contains the functions
> Shift_Left
> Shift_Right
> Shift_Right_Arithmetic
> Rotate_Left
> Rotate_Right

Yes, but Interfaces was added in 95. The sad fact is that modular types,
bitwise operations, and shifts were not part of the Ada 83 definition.

Re: bit shift

[John McCabe]

On 25 Feb 2002 10:08:25 -0800, dewar@gnat.com (Robert Dewar) wrote:

>Not that I blame him, at this stage, seven years after
>the Ada 95 standard has been issued, it seems a pity
>that anyone has to struggle with the use of an obsolete
>language :-)

As you may remember, one of the big deals about Ada was
maintainability and, as you may also remember, one of the other big
deals was about using it for projects that are likely to have a
lifespan of decades rather than the few weeks that you get with other
fly-by-night language based projects :-) So it is not surprising that
there are a significant number of people out there who will be
required to maintain and enhance Ada 83 systems without risking the
jump to Ada 95.