🚀 go-pugleaf

Max Welton wrote:
> 
> mtm4@rsvl.unisys.com (Michael McCormick) wrote:
> >"W. Dicks" <wd@isis.co.za> shared the following on 13 Mar 96 07:31:13 GMT:
> >
> >>The system that I'm working often needs to know the string
> >>value of an enum. e.g. enum week{MON=1, ..., SUN} it; it =
> >>TUE;
> >>Then when this enum is passed as a parameter the function
> >>should return the string based on the enum. For instance,
> >>weekImage(it) will return "TUE". Is it not possible that such
> >>a functionality can be built into enums?
> >
> >What you are essentially asking for is language support for converting
> >a label into a string respresentation of its name.  That is a very
> >unusual feature to find in any language, since it would require the
> >compiler to place the symbolic dictionary in the executable file.  I
> >don't think there's a snowball's chance of this getting into C++.
> 
> It's not _that_ unusual. Ada has had this feature starting with
> Ada-83 (the 'image attribute).

Very true; however, Ada also gurantees some things about scalar 
values that do not apply to C++ enums:
1. You can determine the order of a scalar value in its sequence
2. AFAIK, no two members of the same scalar type can have the same
   underlying representation.

As a result, Ada lets you use a scalar type as an array index,
and compute the successor / predecessor from a given value. In
C++, you cannot do this.  For example:

  enum Code { ready=0, idle = 0, run, halt };

  const char *image( Code value );

how would you handle:
   cout << image( (Code) 0 );


Now if we wanted to guarantee the properties of uniqueness in value 
and sequence in C++, we could do all of these other things, as well. 
-- 
Russell Gold         | (609) 727-2219    
ADP, Inc.            | goldr@bis.adp.com
201 E. Park Dr.      | russgold@ACM.org                  
Mt. Laurel, NJ 08054 | russgold@aol.com
---
[ comp.std.c++ is moderated.  To submit articles: try just posting with      ]
[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu         ]
[ FAQ:      http://reality.sgi.com/employees/austern_mti/std-c++/faq.html    ]
[ Policy:   http://reality.sgi.com/employees/austern_mti/std-c++/policy.html ]
[ Comments? mailto:std-c++-request@ncar.ucar.edu                             ]