On Thu, Oct 2, 2008 at 3:31 PM, Joel de Guzman <joel@boost-consulting.com> wrote:
Giovanni Piero Deretta wrote:
On Thu, Oct 2, 2008 at 1:10 PM, Joel de Guzman
OK, I'm really really missing something:
#include <iostream> #include <vector> #include <boost/spirit/include/phoenix_core.hpp> #include <boost/spirit/home/phoenix/stl.hpp> #include <boost/spirit/include/phoenix_operator.hpp>
using namespace boost::phoenix;
struct foo { typedef void result_type; void operator()(int x) const{ std::cout << x << std::endl; } };
namespace px = boost::phoenix;
int main() { std::vector<int> r(10, 1); foo f; px::for_each(px::arg_names::arg1, f)(r); return 0;
}
This compiles just fine and prints 1 ten times.... I do not need bind to use 'f', it is a perfectly fine unary function object. Phoenix has no business messing with it :)
Aha! You've just uncovered an undocumented feature that I was working on. In phoenix1 and in an experimental version of the scopes, this is actually valid:
for_each(_1, val(f))(r);
Phx always captures by value, so f is essentially val(f) and val(f)() *is* the f itself. Notice the extra nullary function application.
(aside: I'm actually surprised that this feature got in. Some tests by Dan Marsden even takes advantage of it).
*scratches head* Is it really undocumented? Look at http://tinyurl.com/4lnlh3 , the section about Values " add(arg1, 6) Passing a second argument, 6, an actor<value<int> > is implicitly created behind the scenes. This is also equivalent to: add(arg1, val(6)) " Besides, this is the behavior one would expect (as it mimics std::bind).
:-) You must be smiling now imagining me slapping my head! :-)
:) Anyways, from your last post, I see that we basically agree on lambda[] behavior, so I'll stop here. -- gpd