🚀 go-pugleaf

In article <49r5vc$pk2@news.aloha.com> jching@aloha.com "Jimen Ching" writes:

 [standard switch statement]

 > This is valid for C and C++.  So for the above premise of C++, I should
 > also be able to do the following as well:
 > 
 > class internal_type
 >         {
 >         friend bool operator==(const internal_type &lhs, const internal_type
 >  &rhs)
 >                 { return lhs.data == rhs.data; }
 > public:
 >         internal_type(char c = '0') : data(c) {}
 > private:
 >         char data;
 >         };
 > 
 > internal_type const a('a');
 > internal_type const b('b');
 > internal_type const c('c');
 > 
 > f(internal_type &it)
 >         {
 >         switch (it)
 >                 {
 >                 case a: /* do something... */ break;
 >                 case b: /* do something... */ break;
 >                 default: /* do something... */ break;
 >                 }
 >         }

Why? Given that an important feature of a switch statement is that the
target labels are unique, how do you intend to determine this at compile
time for runtime expressions? Don't forget that C/C++ builtins don't allow
you to runaway w/ the show as you've suggested: floats and pointers are not
switchable [Sun used to support switching on floats, but pointers could be
kind of amusing, so perhaps next 1st April...].

 > If C++ lived up to its promise, why can't I do the above?

It lives up to its promises because it _doesn't_ do the above ;->

[example omitted]

Sounds like enums to me -- you've got all the language you need to do the job.
_______________________________________________________________________

  Kevlin A P Henney        2sdg Ltd        kevlin@two-sdg.demon.co.uk
  "What happens to the hole when the cheese is gone?"  Bertolt Brecht
_______________________________________________________________________


---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]