Re: Simplest way to protect a variable ?

[Peter Amey <peter.amey@praxis-cs.co.uk>]

Reinert Korsnes wrote:
> 
> Hi,
> 
> Let's say I initiate a "global" variable, A (for example an array), by
> calling a procedure (which may read data from a file).  And I want to be
> sure that the content (value) of this variable is not changed by
> another procedure.  The variable is "global" in the sense that it is
> available in many many other routines.
> 
> I may have several co-programmers I do not trust :-)
> 
> What is the simplest way to do this (in Ada) ?
> 

I don't know if it is the easiest way, but you could have a Boolean
"Already_Initialised" flag in the package that owns the array.  This
would be set to False during elaboration of the package body.  Your
Initialise procedure would refuse to do anything if Already_Initialised
is set to True and would set it to True after performing the first and
only update of the array.  The array would, of course, also have to be
in the package body (allowing read access via exported subprograms) in
order to prevent any direct updating of it.

Peter