🚀 go-pugleaf

Steve Clamage wrote:
> 
> Yes, there are times when you would like to be able to bind an rvalue
> to a non-const reference, since the only things you care about are
> sure to happen anyway. For example, given a class T:
>         T f1();     // f1 returns a T rvalue
>         f1().foo(); // ok only if foo is a const member function of T

I find this very surprising; perhaps I'm misunderstanding you. This seems
to disallow some very useful techniques.

As an example, suppose I have a string class with some member functions:

    class String {
      public:
        String Substring(int start, int length) const;
          // Extract a substring
        const String& LowerCase();
          // Convert to lower case, and return a const reference to *this
    };

Are you saying I can't write something like:

    String foo, bar;
    foo = bar.Substring(1, 10).LowerCase();

(i.e. the call to Substring() returns a temporary, which is then converted
to lower case, and copied to foo via String::operator= before the temp is
destroyed -- at least, that's what I thought would happen)

I use this sort of technique frequently, and neither of the compilers I use
(Symantec C++ 7.21 and IBM Visual Age C++ 3.0) raise any objection (IBM's
class library explicitly encourages this sort of thing, in fact).

Have I (and IBM and Symantec) got it wrong, or have I just misunderstood
what you wrote? If my code *is* legal, could you explain how it differs
from yours, which seems to be doing exactly the same thing?

-- 
Ross Smith ........................................ Wellington, New Zealand
Home: <mailto:alien@netlink.co.nz> ... Work: <mailto:ross.smith@nz.eds.com>
"I keep my ear very close to the ground, and in consequence I listen to a
lot of dog crap."                                           -- Alexei Sayle
---
[ 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                             ]