Re: [vox] unions [was: ACM article: 'Study: IT Budgets Opening Up to Linux']

[Micah Cowan <mMAPSicah@cowanbox.com>]

On Fri, Aug 24, 2001 at 02:48:38PM -0700, Jeff Newmiller wrote:
> On Fri, 24 Aug 2001, Gabriel Rosa wrote:
> 
> > On Fri, 24 Aug 2001, Peter Jay Salzman wrote:
> > 
> > > btw, in all my years of coding C, i just used a union for the first time.
> > > i feel like celebrating.  :)   also wrote my first lex program.   now the
> > > big trick will be writing the bison companion.  oi vey.
> > >
> > 
> > I can think of many uses for them, but none in projects that I want to
> > undertake.  Conceptually, they are very cool, but as one of my cs profs said
> > (loosely), "In 15 years of C, I've seen 1 person use a union for a good
> > reason".
> 
> In 15 years, I have used them a couple of times "for a good reason".  
> Most interesting one was in a menu datastructure in an embedded C program.  
> Kept data requirements small and allowed "polymorphic" data handling.  In
> other cases, I setup various implementation-specific data format
> converters with them.
> 
> But yes, good uses are rare.
> 
> > Congrats! ;)
> 
> Seconded ... and we won't even ask if your reasons were pure. :)

He used a union for the type of semantic values in his bison code -
the only way to have values of different types for different tokens in
bison.

Micah