phoenix_example.cpp

#include <boost/phoenix.hpp>

int main()
{
    using boost::phoenix::arg_names::arg1;
    using boost::phoenix::arg_names::arg2;
    using boost::phoenix::arg_names::arg3;
    using boost::phoenix::local_names::_a;
    using boost::phoenix::local_names::_b;
    using boost::phoenix::lambda;
    using boost::phoenix::bind;

    // how should i define myplus, mymult and myinit, so that
    // expr1 is arg1 + myplus_f<double>(3.0)(1,arg2) + mymult_f<double>(3.0)(2,arg3)
    auto myplus = lambda(_a = arg1, _b = arg2)[arg1 + _a + _b];
    auto mymult = lambda(_a = arg1, _b = arg2)[arg1 * _a * _b];

    auto myinit = bind(arg1, arg2);

    auto expr0 = lambda[arg1] + myplus(1,arg2) + mymult(2,arg3);
    auto expr1 = myinit( expr0, 3.0 );

    // evaluate expr1 with actual arguments
    double r = expr1(1,2,3);

    // modify the internally held values of myplus_f<double>(3.0) and mymult_f<double>(3.0)
    // so that expr1 becomes equivalent to arg1 + myplus_f<double>(5.0)(1,arg2) + mymult_f<double>(5.0)(2,arg3)
    auto expr2 = myinit( expr0, 5.0 );
    //myreset(expr1, 5.0);

    // evaluate with new value members of myplus_f and mymult_f
    double r2 = expr2(1,2,3);
}