Hi all :

I got confused in Doc of boost :: futures and I can't got the point of sort of terms.

The represents in Overvies of Futures like

" Instances can be freely copied and assigned, and boost::shared_future<R>::get() returns a non const reference so that multiple calls to boost::shared_future<R>::get() are safe."

no doubt that a const reference .... are safe.

a non const reference could be changed by external stimuli. isn't ?

Or the key is "Instances can be freely copied" , so that we can say "are safe"?