Re: Flags in Ada?

[tmoran@bix.com]

Some downsides of using 9X modular types:

 Console.Control := Start_Read_Bit;
may look correct, but perhaps what you really wanted was
 Console.Control := Console.Control or Start_Read_Bit;

Using records, those two are done with less ambiguity with
 Console.Control := Start_Read_OP_Code;
 Console.Control.Start_Read := True;

>...  a measure of safety.  The compiler will complain if you
>use a Status_Byte mask on the Control register, or vice-versa.

But    Console.Control := Console.Control*3;   is legal, though
perhaps not what you meant to code.  And there is a temptation
to do arithmetic (shift, for instance) to accomplish things.
In some circumstances that's fine, and even a good reason to use
modular types rather than records, but it clearly locks you
into a certain bit representation.  There are plenty of programmers
in the world who will do 'clever' arithmetic to juggle bits. :(