Re: bitwise comparators

[Jeff Carter <jrcarter001@my-deja.com>]

In article <3880D375.7E363123@hotmail.com>,
  Alexander Van Hecke <alexke@hotmail.com> wrote:
> hello,
>
> I want to do the following :
> OK_to_proceed : BOOLEAN := FALSE;
> data : Unsigned_8;
>
> while (not OK_to_proceed) loop
>     -- do stuff
>     OK_to_proceed := (data BITWISE AND 2#1#);
> end loop;
>
> so I want to exit the loop if bit one of data is set, but I don't know
> what the bitwise and is!

If Unsigned_8 is a modular type, such as Interfaces.Unsigned_8, then
the operator "and" performs a bitwise and between values of the type:

   Data and 1

The result of this is of type Unsigned_8. You have a number of options
to convert this to Boolean:

   OK_To_Proceed := Boolean'Val (Data and 1);

is probably the best. Others include comparing the result to 1 (OK) and
using an unchecked conversion (not recommended).

I think that

loop
   exit when OK_To_Proceed;

is easer to read and understand than the negative logic used with a
while loop.
--
Jeff Carter
"Now go away or I shall taunt you a second time."
-- Monty Python and the Holy Grail


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