Re: [Boost-users] [phoenix] Basic recursive function.

13 Apr 2011

      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.

Re: [Boost-users] [phoenix] Basic recursive function.

Thomas Heller