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

["jimmaureenrogers@worldnet.att.net" <jimmaureenrogers@worldnet.att.net>]

Jeffrey R. Carter wrote:
> jimmaureenrogers@worldnet.att.net wrote:
> >
> > I guess that depends upon your definition of bit-wise operations.
> > Very few languages support direct indexing of an array of bits.
> > The equivalent access operations are a lot of nasty bit masking
> > an bit shifting operations.
>
> Indeed. My definition is bitwise and, or, and the like. Accessing
> individual bits is not included (though masking certainly is). I guess
> we should ask for the OP's definition.
>
> However, your example works exactly the same if the array is not packed,
> so the fact that the Boolean values are stored as individual bits is a
> side effect of your desire to save space by packing the array, not a
> need to access individual bits, so I would argue that it is not an
> example of bitwise operations, even if accessing individual bits is
> included in the definition.

Actually it does not work exactly the same. The algorithm is
exactly the same, and the same numbers are produced, but the
packed array of bits executes faster on my machine by a factor
of 3 and uses significantly less space (by a factor of 8).

I used a packed array of boolean specifically so that I could
store my flags in individual bits. How much more motivation
could I have to use individual bits?

Your definition of bit-wise appears to me to be based upon the
desire to use a low level abstraction to access the bits. My
definition includes all abstractions that allow access to
individual bits.  When I only programmed in C, I only
thought of bit-wise access in low level abstractions. Since I
have programmed in Ada I think of bit-wise operations in
many abstraction levels.

One of the virtues of Ada is that it allows me to use the
abstraction level most appropriate for my immediate
needs when dealing directly with individual bits or
groups of bits.

Jim Rogers

"Bring me a shrub."