Re: (off-topic) RE: [Doxygen-users] Documenting IDL

[Hendrik S. <Do...@HS...>]

"Stephen Goudge" <ste...@pi...> wrote:

> [...]
> I did originally have an operator int() that could be used in if-statements,
> which worked fine using VC++2 through to VC++4; then a client bought VC++5 and
> it became ambiguous (I forget the precise reason why), so everything switched to
> IsValid() from then on.

  'int' seems like one of the most troublesome ideas. 
  (What's 'spa+spb' to become then?) 

> [...]
> Even with a decent compiler, there is the vexed question of what the cast
> operator should be casting _to_ - you don't really want to return another
> pointer type, as that looks too much like you're providing a backdoor. These
> days, 'bool' would be a reasonable choice (now that the compilers actually
> support 'bool'). The best choice would be the mythical 'logical' type that 'if',
> 'while' etc use, but that isn't available :-(

  Oh, but that's available: It's named 'bool'. 
  But 'bool' isn't all that good either, because it's an 
  arithmetic type. (Or was it convertible into one?) 
  You could thus write 'sp+5' and get funny results. 

  In his book "Modern C++ Design" Andrei Alexandrescu 
  discusses this issue. His idea (typing from memory): 

  template<class T>
  class SmartPtr {
    private: 
      class Tester {
        void operator delete(void*);
      };
    public: 
      operator Tester*() const 
      {
        if( !IsValid() ) 
          return NULL;
        static Tester tester;
        return tester;
      }
      // ... 
  };

  (The private 'operator delete()' is there to prevent 
  users from trying to delete the result of calling the 
  convertion operator.) 

  I have not used this yet, so I don't know whether it's 
  really as great an idea as it seemed to me. 

> Stephen Goudge

  Schobi