Re: How do you bitwise operations in Ada '83 and '95

[Stephen Leake <stephen_leake@acm.org>]

Simon Wright <simon@pushface.org> writes:

> Stephen Leake <stephen_leake@acm.org> writes, responding to me:
>
>>> I have a feeling that shift&mask ends up more understandable 
>>
>> Never.
>>
>>> and reviewable.
>>
>> In Ada 95, maybe. In Ada 2005, not.
>
> Really, understandable and reviewable are very similar, so I don't see
> how something could be (possibly) more reviewable while never more
> understandable.

Hmm. To me, "understandable" means "expressed in terms I am familiar
with, using idioms I am familiar with, and unambiguous". Or something
like that.

While "reviewable" means "traceable to source documentation".

So if I am familiar with the Ada 95 idiom for endianness-independent
rep clauses, they are "understandable". But because they are complex,
they may be less reviewable. I've never done a _formal_ review (trace to
source docs) of any software, so I'm on shaky ground here.

> Seriously, the C
>
>   field = (longword >> 15) & 0x3f;
>
> is pretty clear.

At the bit level, yes. But if the 7 bits are supposed to represent
some object, actual names would be far preferable.

-- 
-- Stephe