Re: Using Global Variables

[cis.ohio-state.edu!news.sei.cmu.edu!lph@ucbvax.Berkeley.EDU (Larry Howar]

Procedural data interfaces show up in many object-oriented designs as services
which objects provide for accessing their instance variables.  Compilers vary
in their abilities to inline and optimize such interfaces.  Shared data (as
variable objects declared in library-level Ada packages) can be a more
efficient alternative to procedurally accessed data, especially when nothing
is really being hidden behind the procedural facade.

We have been involved in the design of several large, real-time Ada
applications (flight simulators) which have used shared memory extensively.
I'm happy to report that the bogeyman has not come and carted us off.  These
applications have realized their engineering goals of modifiability and ease
of integration -- as well as efficiency.  They are among the largest real-time
Ada applications we're aware of.  I personally suggest being wary of anyone
wishing to raise the use of shared variables to the status of mortal sin.



 Larry Howard  (lph@sei.cmu.edu)                       |
 Software Engineering Institute, Carnegie Mellon Univ. | Vera pro gratiis.
 Pittsburgh, PA 15213-3890   (412) 268-6397/5857 (fax) |