Re: Postfix is slower than postfix: how likely?

Francis Glassborow wrote:


It is commonly believed that the postfix operator SHOULD make a copy,
but should it really? It can also return a cheap proxy that increments
the subject upon destruction, in case the subject is expensive to
copy.

class big
{
     // ...

     class proxy
     {
         big* const subject;

     public:
         explicit proxy(big* p) : subject(p) { }
         ~proxy() { ++*subject; }

         operator big&() const { return *subject; }

         // to be complete and allow ++*i++, (i++)->foo(), etc.
         big::pointer operator->() const { return &**subject; }
         big::reference operator*() const { return **subject; }
     };

     big& operator++() { /* the usual prefix increment */ }
     proxy operator++(int) { return proxy(this); }
};

I tested this on a "big" object whose postfix had been 15 times slower
than prefix before, and observed no statistically significant
difference
in the speed between the two.

Maybe this could be a standard idiom for implementing postfix
operators? :)