🚀 go-pugleaf

John Max Skaller (maxtal@suphys.physics.su.oz.au) wrote:

|>     Temporaries are rvalues and so non-const references cannot be
|> bound to them by non-member functions, so they cannot be
|> modified (without a const_cast<>), and so they cannot 
|> transfer ownership (which is a destructive operation).

|>     A solution is to provide a member function:

|>     struct auto_ptr { ...
|>        auto_ptr<T> &ref() { return *this; }
|>        ......
|>     };

|> and now:

|>     auto_ptr<int> f();
|>     auto_ptr<int> p(f().ref());

|> This is a way of converting a non-const rvalue into
|> a non-const lvalue. It is invasive (requires a member function)
|> but it is safe, which a const_cast<> is not.

Just curious: in what way is this any safer than using a const_cast in
the implementation of auto_ptr<T>::operator=()?
-- 
James Kanze           (+33) 88 14 49 00          email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs Bourgeois, 67000 Strasbourg, France
Conseils, études et réalisations en logiciel orienté objet --
              -- A la recherche d'une activité dans une region francophone

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