extern_pdf definition

[scarrazza]

As discussed some time ago, I would suggest to define:

typedef std::function<void(double const&,double const&, size_t const&, real*)> extern_pdf;

So, the user can allocate PDF sets using the LHAPDF6 interface initialized in a well defined container:

class MyPDF
{
public:
  MyPDF(string const& pdfset): { pdf_ = LHAPDF::mkPDFs(pdfset); }
  extern_pdf xfx(double const& x, double const& Q, size_t const& n, real *pdf)
  {
     for (int i = 0; i < 13; i++) res[i] = pdf_[n]->xfxQ(i-6,x,Q);
     return;
  }
private:
  vector<LHAPDF::PDF*> pdf_;
};

int main()
{
  MyPDF pdf("NNPDF30_nlo_as_0118");
   ...
  NNPDF::FKTable FK(infile);
  NNPDF::real* results = new NNPDF::real[FK.GetNData()];
  FK.Convolute(pdf.xfx, 1, results);
}

However this approach requires c++11 and this is potential issue for applgrid.

[nhartland]

Yeah, this is certainly nicer but I don't know if it'd cause problems for APPLgrid.