How to call non static member function from static member function in this particular case-CodePudding

I would like to call the xupv() method from inside func(), but it fails with the following error:

error: cannot call member function ‘auto f(double, double)::Local_::xupv(double)’ without object

#include <iostream>
#include <iomanip>
#include <cmath>
#include <fstream>
#include "QCDNUM/QCDNUM.h"
#include <boost/math/quadrature/trapezoidal.hpp>
#include <vector>

using boost::math::quadrature::trapezoidal;

using namespace std::complex_literals;
using std::cout;
using std::end;

double M = 932.17;
double B = 1.0 / 73.0;
double m_u = 162;
double m_d = 81;
double V = 4.0 / 3.0 * 3.14159 * pow(0.0056, 3);
double R = 0.0056;

auto f(double m, double n){

    class Local_
    {
    public:
      int a;
      int b;
      // All local functions go here:
      //
      auto xupv( double x )
      {
         auto z = [&](double E){
            auto a_1 = a*b*E
            return a_1 
         };
         auto e = trapezoidal(z, x * M / 2.0, M / 2.0);
         auto d = pow(x, 2) * pow(M, 2) / 2.0;
         return e * d;
      };


      static auto func(int *ipdf, double *x)
      {
        int i = *ipdf;
        double xb = *x;
        double f = 0;
        if (i == 0)
            f = 0;
        if (i == 1)
            f = xupv(xb);
        if (i == 2)
            f = 0;
        if (i == 3)
            f = 0;
        if (i == 4)
            f = 0;
        if (i == 5)
            f = 0;
        if (i == 6)
            f = 0;
        if (i == 7)
            f = 0;
        if (i == 8)
            f = 0;
        if (i == 9)
            f = 0;
        if (i == 10)
            f = 0;
        if (i == 11)
            f = 0;
        if (i == 12)
            f = 0;
        return f;
      };
    } local;

    local.a = m;
    local.b = n;

// -----------------------------------------------------------

    int ityp = 1, iord = 3, nfin = 0;                       // unpol, NLO, VFNS
    double as0 = 0.364, r20 = 2.0;                          // input alphas
    double xmin[] = {1.e-4, 1.e-3, 1.e-2, 1.e-1};           // x-grid
    int iwt[] = {1, 1, 1, 1}, ng = 4, nxin = 100, iosp = 3; // x-grid
    int nqin = 60;                                          // mu2-grid
    double qq[] = {1e0, 15}, wt[] = {1e0, 1e0};             // mu2-grid
    double q2c = 3, q2b = 25, q0 = 1;                       // thresholds, mu20
    double x = 1, q = 15, qmz2 = 8315.25, pdf[13];

    double def[] = // input flavour composition
        // tb  bb  cb  sb  ub  db   g   d   u   s   c   b   t
        {0., 0., 0., 0., 0., -1., 0., 1., 0., 0., 0., 0., 0., // 1=dval
         0., 0., 0., 0., -1., 0., 0., 0., 1., 0., 0., 0., 0., // 2=uval
         0., 0., 0., -1., 0., 0., 0., 0., 0., 1., 0., 0., 0., // 3=sval
         0., 0., 0., 0., 0., 1., 0., 0., 0., 0., 0., 0., 0.,  // 4=dbar
         0., 0., 0., 0., 1., 0., 0., 0., 0., 0., 0., 0., 0.,  // 5=ubar
         0., 0., 0., 1., 0., 0., 0., 0., 0., 0., 0., 0., 0.,  // 6=sbar
         0., 0., -1., 0., 0., 0., 0., 0., 0., 0., 1., 0., 0., // 7=cval
         0., 0., 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,  // 8=cbar
         0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,  // 9=zero
         0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,  // 10=zero
         0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,  // 11=zero
         0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.}; // 12=zero

    int nx, nq, id1, id2, nw, nfout, ierr;
    double eps;
    int lun = 6;
    string outfile = " ";

    QCDNUM::qcinit(lun, outfile);                    // initialize
    QCDNUM::gxmake(xmin, iwt, ng, nxin, nx, iosp);   // x-grid
    QCDNUM::gqmake(qq, wt, 2, nqin, nq);             // mu2-grid
    QCDNUM::wtfile(1, "../weights/unpolarised.wgt"); // calculate weights
    QCDNUM::setord(iord);                            // LO, NLO, NNLO
    QCDNUM::setalf(as0, r20);                        // input alphas
    int iqc = QCDNUM::iqfrmq(q2c);                   // charm threshold
    int iqb = QCDNUM::iqfrmq(q2b);                   // bottom threshold
    QCDNUM::setcbt(nfin, iqc, iqb, 999);             // thresholds in the VFNS
    int iq0 = QCDNUM::iqfrmq(q0);                    // start scale

    QCDNUM::evolfg(11, local.func, def, iq0, eps);           // evolve all pdf's

    QCDNUM::allfxq(1, x, q, pdf, 0, 1);              // interpolate all pdf's
    auto res = (pow(2.0 / 3.0, 2)) * (pdf[8]   pdf[4])   (pow(1.0 / 3, 2)) * (pdf[7]   pdf[5])   (pow(1 / 3.0, 2)) * (pdf[9]   pdf[3]);
    cout << res << endl;
}

int main()
{
    f(5, 6);
    return 0;
}

I tried making func() non-static and using this, but then func() cannot be passed to this line below:

QCDNUM::evolfg(11, local.func, def, iq0, eps);

CodePudding user response：

The only way for the static func() to use the non-static xupv() is to give func() access to the local object. Passing the object as a parameter is not an option with the QCDNUM library, so you will have to use a global/static pointer instead, eg:

// move this into global scope...
class Local_
{
public:
  ...
  static Local_ *pThis; // <-- add this

  Local_() { pThis = this; }

  auto xupv( double x )
  { 
     return ...;
  }

  static auto func(int *ipdf, double *x)
  {
     ...
     if (i == 1)
        f = pThis->xupv(xb); // <-- use it here
     ... 
     return ...;
  } 
}; 

Local_* Local_::pThis = nullptr;

auto f(double m, double n){

    Local_ local;
    ...
    QCDNUM::evolfg(..., local.func, ...);
    ...
}