At Wed, 13 Apr 2011 16:10:12 +0100, Robert Jones wrote:

I'm a newbie to Phoenix, just exploring, but I guess my intent in this code is obvious. Can anyone tell me what I'm doing wrong?

Thx

- Rob.

#include <iostream> #include #include #include #include

using namespace boost::phoenix; using namespace boost::phoenix::arg_names; using namespace std;

int main() { boost::function factorial; factorial = if_else( _1 == 0, 1, _1 * factorial( _1 - 1 ) );

I think you'd better find a way to store factorial by reference in the phoenix expression, because the value at the time of building is empty. Totally guessing: factorial = if_else( _1 == 0, 1, _1 * ref(factorial)( _1 - 1 ) ); -- Dave Abrahams BoostPro Computing http://www.boostpro.com

On Wednesday, April 13, 2011 05:10:12 PM Robert Jones wrote:

I'm a newbie to Phoenix, just exploring, but I guess my intent in this code is obvious. Can anyone tell me what I'm doing wrong?

Thx

- Rob.

#include <iostream> #include #include #include #include

using namespace boost::phoenix; using namespace boost::phoenix::arg_names; using namespace std;

int main() { boost::function factorial; factorial = if_else( _1 == 0, 1, _1 * factorial( _1 - 1 ) );

cout << factorial( 3 ) << endl;

return 0; }

DISCLAIMER: The following is undocumented, might not work and is subject to change without notice. Phoenix V3 (from trunk) has experimental support for recursing into itself: #include #include #include #include #include #include #include <iostream> int main() { using boost::phoenix::_this; using boost::phoenix::arg_names::_1; boost::function factorial = if_else( _1 <= 1 , 1 , _1 * _this(_1 - 1) ); std::cout << factorial( 3 ) << std::endl; } Have fun playing with it ;) I don't accept bugfixes for this feature cause i know it is not working in every case ... still needs a little work. If you encounter compile errors, add some dummy phoenix expression at the end of the recursing branch.