Re: [Boost-users] [signals] maximum combiner example calls slot twice

On Friday 24 April 2009, Dominique Devienne wrote:

In http://www.boost.org/doc/libs/1_38_0/doc/html/signals/tutorial.html, once I read:

"The input iterators passed to the combiner transform dereference operations into slot calls"

I realized that the maximum<T> combiner introduced earlier is implemented using:

if (max_value < *first) max_value = *first;

Which ends up calling the slot twice.

Dereferencing a slot call iterator multiple times only runs the slot once. After that, it returns a cached copy of the return value.