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 <boost/spirit/include/phoenix_core.hpp> #include <boost/spirit/home/phoenix/operator.hpp> #include <boost/spirit/home/phoenix/statement.hpp> #include <boost/function.hpp>
using namespace boost::phoenix; using namespace boost::phoenix::arg_names; using namespace std;
int main() { boost::function<unsigned( unsigned )> 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 <boost/phoenix/core.hpp> #include <boost/phoenix/scope/this.hpp> #include <boost/phoenix/statement.hpp> #include <boost/phoenix/operator.hpp> #include <boost/phoenix/scope.hpp> #include <boost/function.hpp> #include <iostream> int main() { using boost::phoenix::_this; using boost::phoenix::arg_names::_1; boost::function<unsigned(unsigned)> 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.