On Thu, Oct 7, 2010 at 8:37 PM, Emil Dotchevski <emil@revergestudios.com> wrote:
On Thu, Oct 7, 2010 at 6:22 PM, Peter Dimov <pdimov@pdimov.com> wrote:
Daniel Walker wrote:
void do_stuff(boost::function<int(int)> f) { // ... if(f) { // Remove the exception safety guarantee for this block. boost::unsafe_function<int(int)> g = f; for(int i = 0; i < INT_MAX; ++i) g(i); } // ... }
This example implies that unsafe_function is inherently more efficient, but this need not be so. An empty function may point to throw_bad_function_call instead of NULL.
Right, and what the empty boost::function does needs not be decided at compile time, it can be done in the constructor.
However the empty built-in Boost.Function still does an if(isnull) test on every operator call, whether you assigned something in the constructor or not...